# Bulletin No. 2025–41

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## Record

- **Collection:** Agency decision
- **Document type:** Agency decision

## Text

HIGHLIGHTS
OF THIS ISSUE




Bulletin No. 2025–41
October 6, 2025

These synopses are intended only as aids to the reader in
identifying the subject matter covered. They may not be
relied upon as authoritative interpretations.

ADMINISTRATIVE, INCOME TAX

INCOME TAX

Notice 2025-54, page 479.

Notice 2025-52, page 474.

Optional special per diem rates. This notice provides the
2025-2026 special per diem rates for taxpayers to use in
substantiating the amount of ordinary and necessary business
expenses incurred while traveling away from home. The notice
includes (1) the special transportation industry rate, (2) the
rate for the incidental expenses only deduction, and (3) the
rates and list of high-cost localities for the high-low substantiation method.

EXCISE TAX
Notice 2025-51, page 448.

This Notice of Determinations adds 39 chemical substances
to the list of taxable substances under § 4672 subject to the
tax imposed by § 4671.

Finding Lists begin on page ii.

This notice explains the circumstances under which the fouryear replacement period under section 1033(e)(2) is extended
for livestock sold on account of drought. The Appendix to this
notice contains a list of counties that experienced exceptional,
extreme, or severe drought conditions during the 12-month
period ending August 31, 2025. Taxpayers may use this list to
determine if any extension is available.

Rev. Rul. 2025-19, page 445.

Federal rates; adjusted federal rates; adjusted federal longterm rate, and the long-term tax exempt rate. For purposes of
sections 382, 1274, 1288, 7872 and other sections of the
Code, tables set forth the rates for October 2025.

Rev. Rul. 2025-20, page 447.

Fringe benefits aircraft valuation formula. For purposes of section 1.61-21(g) of the Income Tax Regulations, relating to the
rule for valuing non-commercial flights on employer-provided
aircraft, the Standard Industry Fare Level (SIFL) cents-per-mile
rates and terminal charge in effect for the second half of 2025
are set forth.

The IRS Mission
Provide America’s taxpayers top-quality service by helping
them understand and meet their tax responsibilities and
enforce the law with integrity and fairness to all.

Introduction
The Internal Revenue Bulletin is the authoritative instrument
of the Commissioner of Internal Revenue for announcing official rulings and procedures of the Internal Revenue Service
and for publishing Treasury Decisions, Executive Orders, Tax
Conventions, legislation, court decisions, and other items of
general interest. It is published weekly.
It is the policy of the Service to publish in the Bulletin all substantive rulings necessary to promote a uniform application
of the tax laws, including all rulings that supersede, revoke,
modify, or amend any of those previously published in the
Bulletin. All published rulings apply retroactively unless otherwise indicated. Procedures relating solely to matters of internal management are not published; however, statements of
internal practices and procedures that affect the rights and
duties of taxpayers are published.
Revenue rulings represent the conclusions of the Service
on the application of the law to the pivotal facts stated in
the revenue ruling. In those based on positions taken in rulings to taxpayers or technical advice to Service field offices,
identifying details and information of a confidential nature are
deleted to prevent unwarranted invasions of privacy and to
comply with statutory requirements.
Rulings and procedures reported in the Bulletin do not have the
force and effect of Treasury Department Regulations, but they
may be used as precedents. Unpublished rulings will not be
relied on, used, or cited as precedents by Service personnel in
the disposition of other cases. In applying published rulings and
procedures, the effect of subsequent legislation, regulations,
court decisions, rulings, and procedures must be considered,
and Service personnel and others concerned are cautioned

against reaching the same conclusions in other cases unless
the facts and circumstances are substantially the same.
The Bulletin is divided into four parts as follows:
Part I.—1986 Code.
This part includes rulings and decisions based on provisions
of the Internal Revenue Code of 1986.
Part II.—Treaties and Tax Legislation.
This part is divided into two subparts as follows: Subpart A,
Tax Conventions and Other Related Items, and Subpart B,
Legislation and Related Committee Reports.
Part III.—Administrative, Procedural, and Miscellaneous.
To the extent practicable, pertinent cross references to these
subjects are contained in the other Parts and Subparts. Also
included in this part are Bank Secrecy Act Administrative
Rulings. Bank Secrecy Act Administrative Rulings are issued
by the Department of the Treasury’s Office of the Assistant
Secretary (Enforcement).
Part IV.—Items of General Interest.
This part includes notices of proposed rulemakings, disbarment and suspension lists, and announcements.
The last Bulletin for each month includes a cumulative index
for the matters published during the preceding months. These
monthly indexes are cumulated on a semiannual basis, and are
published in the last Bulletin of each semiannual period.

The contents of this publication are not copyrighted and may be reprinted freely. A citation of the Internal Revenue Bulletin as the source would be appropriate.

October 6, 2025 

Bulletin No. 2025–41

Part I
Section 1274.—
Determination of Issue
Price in the Case of Certain
Debt Instruments Issued for
Property
(Also Sections 42, 280G, 382, 467, 468, 482, 483,
1288, 7520, 7872.)

Rev. Rul. 2025-19
This revenue ruling provides various prescribed rates for federal income

Annual
AFR
110% AFR
120% AFR
130% AFR

3.81%
4.19%
4.57%
4.96%

AFR
110% AFR
120% AFR
130% AFR
150% AFR
175% AFR

3.87%
4.25%
4.65%
5.04%
5.83%
6.81%

AFR
110% AFR
120% AFR
130% AFR

4.73%
5.22%
5.70%
6.17%

Short-term adjusted AFR
Mid-term adjusted AFR
Long-term adjusted AFR

Bulletin No. 2025–41

tax purposes for October 2025 (the
current month). Table 1 contains the
short-term, mid-term, and long-term
applicable federal rates (AFR) for the
current month for purposes of section
1274(d) of the Internal Revenue Code.
Table 2 contains the short-term, midterm, and long-term adjusted applicable federal rates (adjusted AFR) for the
current month for purposes of section
1288(b). Table 3 sets forth the adjusted
federal long-term rate and the longterm tax-exempt rate described in section 382(f). Table 4 contains the appro-

priate percentages for determining the
low-income housing credit described in
section 42(b)(1) for buildings placed in
service during the current month. However, under section 42(b)(2), the applicable percentage for non-federally subsidized new buildings placed in service
after July 30, 2008, shall not be less
than 9%. Finally, Table 5 contains the
federal rate for determining the present
value of an annuity, an interest for life
or for a term of years, or a remainder or
a reversionary interest for purposes of
section 7520.

REV. RUL. 2025-19 TABLE 1
Applicable Federal Rates (AFR) for October 2025
Period for Compounding
Semiannual
Quarterly
Short-term
3.77%
3.75%
4.15%
4.13%
4.52%
4.49%
4.90%
4.87%
Mid-term
3.83%
3.81%
4.21%
4.19%
4.60%
4.57%
4.98%
4.95%
5.75%
5.71%
6.70%
6.64%
Long-term
4.68%
4.65%
5.15%
5.12%
5.62%
5.58%
6.08%
6.03%

Annual
2.88%
2.93%
3.58%

REV. RUL. 2025-19 TABLE 2
Adjusted AFR for October 2025
Period for Compounding
Semiannual
2.86%
2.91%
3.55%

445

Quarterly
2.85%
2.90%
3.53%

Monthly
3.74%
4.11%
4.48%
4.85%
3.80%
4.17%
4.56%
4.93%
5.68%
6.61%
4.64%
5.10%
5.56%
6.00%

Monthly
2.84%
2.89%
3.52%

October 6, 2025

REV. RUL. 2025-19 TABLE 3
Rates Under Section 382 for October 2025
Adjusted federal long-term rate for the current month
Long-term tax-exempt rate for ownership changes during the current month (the highest of the adjusted federal
long-term rates for the current month and the prior two months.)

3.58%
3.65%

REV. RUL. 2025-19 TABLE 4
Appropriate Percentages Under Section 42(b)(1) for October 2025
Note: Under section 42(b)(2), the applicable percentage for non-federally subsidized new buildings placed in service after
July 30, 2008, shall not be less than 9%.
Appropriate percentage for the 70% present value low-income housing credit
8.00%
Appropriate percentage for the 30% present value low-income housing credit
3.43%
REV. RUL. 2025-19 TABLE 5
Rate Under Section 7520 for October 2025
Applicable federal rate for determining the present value of an annuity, an interest for life or a term of years,
or a remainder or reversionary interest

Section 42.—Low-Income
Housing Credit
The applicable federal short-term, mid-term,
and long-term rates are set forth for the month of
October 2025. See Rev. Rul. 2025-19, page 445.

Section 280G.—Golden
Parachute Payments
The applicable federal short-term, mid-term,
and long-term rates are set forth for the month of
October 2025. See Rev. Rul. 2025-19 page 445.

Section 382.—Limitation
on Net Operating Loss
Carryforwards and
Certain Built-In Losses
Following Ownership
Change
The adjusted applicable federal long-term rate
is set forth for the month of October 2025. See Rev.
Rul. 2025-19, page 445.

Section 467.—Certain
Payments for the Use of
Property or Services
The applicable federal short-term, mid-term,
and long-term rates are set forth for the month of
October 2025. See Rev. Rul. 2025-19, page 445.

Section 468.—Special
Rules for Mining and Solid
Waste Reclamation and
Closing Costs
The applicable federal short-term rates are set
forth for the month of October 2025. See Rev. Rul.
2025-19, page 445.

Section 482.—Allocation
of Income and Deductions
Among Taxpayers
The applicable federal short-term, mid-term,
and long-term rates are set forth for the month of
October 2025. See Rev. Rul. 2025-19, page 445.

4.6%

Section 483.—Interest on
Certain Deferred Payments
The applicable federal short-term, mid-term,
and long-term rates are set forth for the month of
October 2025. See Rev. Rul. 2025-19, page 445.

Section 1288.—Treatment
of Original Issue Discount
on Tax-Exempt Obligations
The adjusted applicable federal short-term, midterm, and long-term rates are set forth for the month
of October 2025. See Rev. Rul. 2025-19, page 445.

Section 7520.—Valuation
Tables
The applicable federal mid-term rates are set
forth for the month of October 2025. See Rev. Rul.
2025-19, page 445.

Section 7872.—Treatment
of Loans With BelowMarket Interest Rates
The applicable federal short-term, mid-term,
and long-term rates are set forth for the month of
October 2025. See Rev. Rul. 2025-19, page 445.

October 6, 2025

446

Bulletin No. 2025–41

Section 61. Gross Income
Defined
26 CFR 1.61-21: Taxation of Fringe Benefits

Rev. Rul. 2025-20
For purposes of the taxation of fringe
benefits under section 61 of the Internal

Revenue Code, section 1.61-21(g) of
the Income Tax Regulations provides a
rule for valuing noncommercial flights
on employer-provided aircraft. Section
1.61-21(g)(5) provides an aircraft valuation formula to determine the value
of such flights. The value of a flight is
determined under the base aircraft valuation formula (also known as the Standard
Industry Fare Level formula or SIFL)
by multiplying the SIFL cents-per-mile

Period During Which the Flight Is Taken

Terminal Charge

rates applicable for the period during
which the flight was taken by the appropriate aircraft multiple provided in section 1.61-21(g)(7) and then adding the
applicable terminal charge. The SIFL
cents-per-mile rates in the formula and
the terminal charge are calculated by the
Department of Transportation (DOT) and
are reviewed semi-annually.
The following chart sets forth the terminal charge and SIFL mileage rates:
SIFL Mileage Rates

7/1/25 - 12/31/25
$53.62

Up to 500 miles
= $.2933 per mile

501-1500 miles
= $.2237 per mile

Over 1500 miles
= $.2150 per mile

DRAFTING INFORMATION
The principal author of this revenue ruling is Kathleen Edmondson of the Office

Bulletin No. 2025–41

of Associate Chief Counsel (Employee
Benefits, Exempt Organizations and
Employment Taxes). For further information regarding this revenue ruling, contact

447

Ms. Edmondson at (202) 317-6798 (not a
toll-free number).

October 6, 2025

Part III
Superfund Tax on Chemical
Substances; Notice of
Determinations to Add
Substances to List of
Taxable Substances
Notice 2025-51
SUMMARY: This notice of determinations modifies the list of taxable substances to include the following 39 substances: acrylonitrile-butadiene rubber
((C4H6)n-(C3H3N)m; n=13.44, m=25.54),
bromo-isobutene-isoprene rubber ((C4H8)
-(C5H7.5Br0.5)m;
n=98.20,
m=1.80),
n
chloroprene rubber, ethylene-propylene-ethylidene norbornene rubber ((C2H4)
-(C3H6)n(C9H12)o; m=56.82, n=40.46,
m
o=2.71), ethylene vinyl acetate (VA < 50%)
((C2H4)n-(C4H6O2)m; n=78.95, m=21.05),
ethylene vinyl acetate (VA ≥ 50%) ((C2H4)
-(C4H6O2)m; n=75.42, m=24.58), hydron
genated acrylonitrile-butadiene rubber
((C4H8)n-(C3H3N)m; n=22.28, m= 38.86),
isobutene-isoprene rubber ((C4H8)n-(C5H8)
; n=99.10, m=0.90), poly(ethylene-prom
pylene) rubber ((C2H4)m-(C3H6)n; m=59.04,
n=40.96), emulsion styrene-butadiene rubber ((C4H6)m-(C8H8)n; m=15.83, n=2.53),
solution styrene-butadiene rubber ((C4H6)
-(C8H8)n; m=67.16, n=32.85), emulsion
m
styrene butadiene rubber ((C4H6)m-(C8H8)
; m=14.14, n=2.26), solution styrene-bun
tadiene rubber ((C4H6)m-(C8H8)n; m=13.31,
n=2.50), hydrogenated acrylonitrile-butadiene rubber ((C4H8)x-(C3H3N)y-(C15H24O)
; x=2,783.05, y=1,907.27, a=5.74), broa
mobutyl isobutylene isoprene rubber
((C4H8)x(C5H8)y(Br2)z; x=7071, y=59,
z=50), chlorobutyl isobutylene isoprene
rubber ((C4H8)x(C5H8)y(Cl2)z); x=7036,
y=88, z=70), DIPE–di-isopropyl ether,
di-isodecyl phthalate, di-isononyl adipate,
di-isononyl phthalate, di-tridecyl phthalate,
ethylene propylene diene (EPDM) rubber
((C2H4)x(C3H6)y(C9H12)z; x=5134, y=2250,
z=98), isodecyl alcohol, isodecyl benzoate,
isooctyl alcohol, linear nonyl phthalate, linear nonyl undecyl phthalate, linear undecyl
phthalate, linear nonyl tri-mellitate, neo
decanoic acid, neo pentanoic acid, nonene, regular butyl rubber ((C4H8)x(C5H8)

October 6, 2025

; x=7036, y=88), tridecyl alcohol, triisononyl tri-mellitate, di-isobutylene, polyisobutylene, styrene-acrylonitrile ((C3H3N)
-(C8H8)s; a=0.26, s=0.74), and acrylonia
trile butadiene styrene ((C3H3N)a-(C4H6)
-(C8H8)s; a=0.16, b=0.10, s=0.74),
b
y

EFFECTIVE DATES: The effective date
for purposes of the tax under section 4671
of the Internal Revenue Code (Code) for
the taxable substances added to the list is
January 1, 2026. For the effective date for
purposes of refund claims under section
4662(e) of the Code for the taxable substances added to the list, see the determination for each substance.
FOR FURTHER INFORMATION
CONTACT: Andrew Clark or Jacob
Peeples at (202) 317-6855 (not a toll-free
number).
SUPPLEMENTARY INFORMATION:
Background
Section 4671(a) of the Code imposes
an excise tax on the sale or use of a taxable
substance by the importer thereof (section
4671 tax). Section 4672(a)(1) of the Code
defines the term taxable substance as any
substance which, at the time of sale or use
by the importer, is listed as a taxable substance by the Secretary of the Treasury or
the Secretary’s delegate (Secretary) on the
list of taxable substances under section
4672(a) (List).
Under section 4672(a)(2), an importer
or exporter of any substance may request
that the Secretary determine whether such
substance should be added to the List as
a taxable substance or should be removed
from the List. Under section 4672(a)(2)
(B) and (a)(4) and (b)(2), the Secretary
is required to add a substance to the List
if the Secretary determines that any taxable chemicals that are listed in section
4661(b) of the Code constitute more than
20 percent of the weight, or more than
20 percent of the value, of the materials
used to produce such substance, which
determination is required under section
4672(a)(2)(B) and (a)(4) to be made based
on the predominant method of production

448

(weight or value test). Section 4672(a)(4)
authorizes the Secretary to remove a substance from the List only if such substance
meets neither the weight nor the value test
of section 4672(a)(2)(B).
Section 4672(a)(3) includes an initial
list of taxable substances. Section 4 of
Notice 2021-66 (2021-52 I.R.B. 901) provides the list of 101 substances that the
Secretary added to the List before November 15, 2021. On May 31, 2024, the Secretary published a Notice of Determination
in the Federal Register (89 FR 47238)
adding polyoxymethylene to the List;
this Notice of Determination was also
published in the Internal Revenue Bulletin as Notice 2024-50 (2024-26 I.R.B.
1789). On August 4, 2025, the Secretary
published a Notice of Determinations in
the Federal Register (90 FR 36520) adding 21 substances to the List; this Notice
of Determinations was also published in
the Internal Revenue Bulletin as Notice
2025-41 (2025-34 I.R.B. 325). Rev. Proc.
2022-26 (2022-29 I.R.B. 90), as modified
by Rev. Proc. 2023-20 (2023-15 I.R.B.
636), provides the exclusive procedures
by which an importer, exporter, or interested person may request a determination
that a particular substance be added to or
removed from the List.
Section 4671(b)(3) authorizes the Secretary to prescribe a tax rate for taxable substances in lieu of the tax rate specified in
section 4671(b)(2). The tax rate prescribed
by the Secretary for a substance added to
the List is calculated by multiplying the
conversion factor for each taxable chemical used in the production of the substance
by the corresponding tax rate for that taxable chemical under section 4661(b), and
adding those results together. Conversion
factors are determined based on the predominant method of production of the substance. See sections 8 and 10.04(8) of Rev.
Proc. 2022-26. Importers are not required
to use the prescribed tax rate for a taxable
substance and may calculate their own rate
under section 4671(b)(1).
Pursuant to Section 4672(a)(4), this
notice of determinations modifies the List
to include the 39 additional taxable substances listed in the Summary of Determinations section of this notice, as explained

Bulletin No. 2025–41

in the Requests to Add Substances to the
List and General Explanation of Determinations sections of this notice. The determination for each specific substance added
to the List is explained in parts 1 through
39 of the Modifications to the List of Taxable Substances section of this notice.
The updated List and prescribed
tax rates for taxable substances will be
included in the instructions to Form 6627,
Environmental Taxes.
Summary of Determinations
On September 15, 2025, the Secretary
determined to add the following substances to the List:
1. Acrylonitrile-butadiene rubber ((C4H6)
-(C3H3N)m; n=13.44, m=25.54)
n
2. Bromo-isobutene-isoprene
rubber
((C4H8)n-(C5H7.5Br0.5)m;
n=98.20,
m=1.80)
3. Chloroprene rubber
4. Ethylene-propylene-ethylidene norbornene rubber ((C2H4)m-(C3H6)
(C9H12)o; m=56.82, n=40.46, o=2.71)
n
5. Ethylene vinyl acetate (VA < 50%)
((C2H4)n-(C4H6O2)m;
n=78.95,
m=21.05)
6. Ethylene vinyl acetate (VA ≥ 50%)
((C2H4)n-(C4H6O2)m;
n=75.42,
m=24.58)
7. Hydrogenated acrylonitrile-butadiene
rubber ((C4H8)n-(C3H3N)m; n=22.28,
m= 38.86)
8. Isobutene-isoprene rubber ((C4H8)
-(C5H8)m; n=99.10, m=0.90)
n
9. Poly(ethylene-propylene)
rubber
((C2H4)m-(C3H6)n; m=59.04, n=40.96)
10. Emulsion styrene-butadiene rubber
((C4H6)m-(C8H8)n; m=15.83, n=2.53)
11. Solution styrene-butadiene rubber
((C4H6)m-(C8H8)n; m=67.16, n=32.85)
12. Emulsion styrene butadiene rubber
((C4H6)m-(C8H8)n; m=14.14, n=2.26)
13. Solution styrene-butadiene rubber
((C4H6)m-(C8H8)n; m=13.31, n=2.50)
14. Hydrogenated acrylonitrile-butadiene
rubber ((C4H8)x-(C3H3N)y-(C15H24O)a;
x=2,783.05, y=1,907.27, a=5.74)
15. Bromobutyl isobutylene isoprene
rubber ((C4H8)x(C5H8)y(Br2)z; x=7071,
y=59, z=50)
16. Chlorobutyl isobutylene isoprene rubber ((C4H8)x(C5H8)y(Cl2)z); x=7036,
y=88, z=70)
17. DIPE–di-isopropyl ether

Bulletin No. 2025–41

18. Di-isodecyl phthalate
19. Di-isononyl adipate
20. Di-isononyl phthalate
21. Di-tridecyl phthalate
22. Ethylene propylene diene (EPDM)
rubber
((C2H4)x(C3H6)y(C9H12)z;
x=5134, y=2250, z=98)
23. Isodecyl alcohol
24. Isodecyl benzoate
25. Isooctyl alcohol
26. Linear nonyl phthalate
27. Linear nonyl undecyl phthalate
28. Linear undecyl phthalate
29. Linear nonyl tri-mellitate
30. Neo decanoic acid
31. Neo pentanoic acid
32. Nonene
33. Regular butyl rubber ((C4H8)x(C5H8)y;
x=7036, y=88)
34. Tridecyl alcohol
35. Tri-isononyl tri-mellitate
36. Di-isobutylene
37. Polyisobutylene
38. Styrene-acrylonitrile
((C3H3N)
-(C
H
)
;
a=0.26,
s=0.74)
a
8 8 s
39. Acrylonitrile
butadiene
styrene
((C3H3N)a-(C4H6)b-(C8H8)s; a=0.16,
b=0.10, s=0.74)
Requests to Add Substances to the List
For each of the substances listed in
the Summary of Determinations section
of this notice, an importer or an exporter
submitted a petition to the IRS in accordance with Rev. Proc. 2022-26 requesting
a determination under section 4672(a)(2)
to add the substance to the List. For each
substance, the petition represented that
taxable chemicals constitute more than 20
percent of the weight of materials used to
produce the substance, based on the predominant method of production.
General Explanation of Determinations
After reviewing the petitions for each
of the substances listed in the Summary of
Determinations section of this notice, the
Secretary determined that taxable chemicals constitute more than 20 percent by
weight of the materials used to produce
the substance, based on the predominant
method of production. Therefore, each
of the substances is added to the List as
required under section 4672(a)(2) and (4).
The Secretary made the determinations to

449

add these substances to the List in accordance with the requirements of section
4672(a)(2) and (4), and pursuant to the
procedures set forth in Rev. Proc. 202226, as modified by Rev. Proc. 2023-20.
The relevant information for each taxable substance is provided in the specific
determinations included in parts 1 through
39 of the Modifications to the List of Taxable Substances section of this notice.
The tax rate for each taxable substance, as
prescribed by the Secretary, is provided in
paragraph (a)(6) of each specific determination. All scientific information provided
in the specific determinations reflects
the information provided by petitioners
as published in each taxable substance’s
respective Notice of Filing.
Classification numbers proposed by
each petitioner are included in paragraph
(b) of each part, after each specific determination. The classification numbers
provided with respect to a taxable substance are not part of the determination
of whether it is added to the List and do
not impact whether such substance is a
taxable substance. Taxpayers may not rely
on classification numbers for any purpose
under sections 4661, 4662, 4671, and
4672, including (but not limited to) identification of a substance as a taxable substance on the List. Classification numbers
may change over time. The Department of
the Treasury (Treasury Department) and
the IRS do not anticipate updating this
document to reflect any such changes.
For purposes of the section 4671 tax,
all the modifications in parts 1 through 39
of the Modifications to the List of Taxable Substances section of this notice are
effective on and after January 1, 2026. For
purposes of refund claims under section
4662(e), see the effective date for each
specific determination in paragraph (a)(5)
(ii) of each of parts 1 through 39 of the
Modifications to the List of Taxable Substances section of this notice.
Modifications to the List of Taxable
Substances
1. Determination to Add Acrylonitrilebutadiene Rubber ((C4H6)n-(C3H3N)m;
n=13.44, m=25.54) to the List
Arlanxeo USA LLC and Arlanxeo Canada Inc., importers and exporters of acrylo-

October 6, 2025

nitrile-butadiene rubber ((C4H6)n-(C3H3N)m;
n=13.44, m=25.54), submitted a petition in
accordance with Rev. Proc. 2022-26 requesting to add acrylonitrile-butadiene rubber
((C4H6)n-(C3H3N)m; n=13.44, m=25.54) to
the List. According to the petition, the taxable chemicals butadiene, propylene, and
ammonia constitute 64.59 percent by weight
of the materials used to produce acrylonitrile-butadiene rubber ((C4H6)n-(C3H3N)m;
n=13.44, m=25.54), based on the predominant method of production.
(a) Determination. Acrylonitrile-butadiene rubber ((C4H6)n-(C3H3N)m; n=13.44,
m=25.54) is added to the list of taxable
substances under section 4672(a). Other
pertinent information is as follows:
(1) Predominant method of production:
The predominant method of producing
acrylonitrile-butadiene rubber is through
a radical polymerization of acrylonitrile
and butadiene in an emulsion process.
Acrylonitrile monomer is produced by the
SOHIO process (i.e., catalytic ammoxidation of propylene).
(2) Stoichiometric material consumption equation:
n C4H6 (butadiene) + m [C3H6 (propylene) + NH3 (ammonia) + 3/2 O2] →
(C4H6)n-(C3H3N)m (acrylonitrile-butadiene rubber) + 3m H2O
(3) Reasons for the determination: The
acrylonitrile-butadiene rubber ((C4H6)
-(C3H3N)m; n=13.44, m=25.54) petition
n
was filed on February 7, 2025. The notice
of filing summarizing the petition and
requesting comments was published in the
Federal Register (90 FR 14684) on April
3, 2025. The Treasury Department and
the IRS received no written comments in
response to the notice of filing. A public
hearing was neither requested nor held.
The Secretary followed the process
in section 4672(a)(2)(B) in making this
determination. A review of the stoichiometric material consumption equation and
other information in the petition shows
that the taxable chemicals butadiene, propylene, and ammonia constitute more than
20 percent by weight of the materials used
in the production of acrylonitrile-butadiene rubber ((C4H6)n-(C3H3N)m; n=13.44,
m=25.54), based on the predominant
method of production. Therefore, the test
in section 4672(a)(2)(B) is satisfied.

October 6, 2025

(4) Date of determination: September
15, 2025.
(5) Effective dates for addition of acrylonitrile-butadiene rubber ((C4H6)n-(C3H3N)
; n=13.44, m=25.54) to the List:
m
(i) Effective date for purposes of the
section 4671 tax (see section 11.01 of Rev.
Proc. 2022-26): January 1, 2026
(ii) Effective date for purposes of refund
claims under section 4662(e) (see sections
11.02 and 11.03 of Rev. Proc. 2022-26, as
modified by section 3 of Rev. Proc. 202320): July 1, 2022
(6) Tax rate prescribed by the Secretary: $9.58 per ton. The conversion factors
for the taxable chemicals used in the production of acrylonitrile-butadiene rubber
((C4H6)n-(C3H3N)m; n=13.44, m=25.54)
are 0.35 for butadiene, 0.52 for propylene,
and 0.21 for ammonia. The tax rate is calculated by adding the products of the conversion factor for each taxable chemical
by the tax rate for that taxable chemical:
((0.35 x $9.74) + (0.52 x $9.74) + (0.21 x
$5.28) = $9.58).
(b) Classification numbers.
(1) The Secretary has no basis to object
to the following proposed classification
numbers:
(i) HTSUS number: 4002.59.0000
(ii) Schedule B number: 4002.59.0000
(iii) CAS number: 9003-18-3
(2) The Secretary is unable to confirm the following proposed classification
numbers: Not applicable.
2. Determination to Add Bromoisobutene-isoprene Rubber ((C4H8)
-(C5H7.5Br0.5)m; n=98.20, m=1.80) to the
n
List
Arlanxeo USA LLC and Arlanxeo
Canada Inc., importers and exporters of
bromo-isobutene-isoprene rubber ((C4H8)
-(C5H7.5Br0.5)m; n=98.20, m=1.80), subn
mitted a petition in accordance with Rev.
Proc. 2022-26 requesting to add bromo-isobutene-isoprene rubber ((C4H8)
-(C5H7.5Br0.5)m; n=98.20, m=1.80) to
n
the List. According to the petition, the
taxable chemicals butylene, bromine,
and sodium hydroxide constitute 97.89
percent by weight of the materials used
to produce bromo-isobutene-isoprene
rubber ((C4H8)n-(C5H7.5Br0.5)m; n=98.20,
m=1.80), based on the predominant
method of production.

450

(a) Determination. Bromo-isobutene-isoprene rubber ((C4H8)n-(C5H7.5Br0.5)
; n=98.20, m=1.80) is added to the list of
m
taxable substances under section 4672(a).
Other pertinent information is as follows:
(1) Predominant method of production:
The predominant method of producing
bromo-isobutene-isoprene rubber involves
reacting a hexane solution of butyl rubber
with elemental bromine. Butyl rubber is
produced via the cationic copolymerization of butylene with isoprene in the presence of a Friedel-Crafts catalyst at low
temperature, around -100°C.
(2) Stoichiometric material consumption equation:
n C4H8 (butylene) + m C5H8 (isoprene) + m/2 Br2 (bromine) + m/2
NaOH (sodium hydroxide) → (C4H8)
(C5H7.5Br0.5)m (bromo-isobutene-ison
prene rubber) + m/2 NaBr + m/2 H2O
(3) Reasons for the determination: The
bromo-isobutene-isoprene rubber ((C4H8)
-(C5H7.5Br0.5)m; n=98.20, m=1.80) petin
tion was filed on February 7, 2025. The
notice of filing summarizing the petition
and requesting comments was published
in the Federal Register (90 FR 14694) on
April 3, 2025. The Treasury Department
and the IRS received no written comments in response to the notice of filing.
A public hearing was neither requested
nor held.
The Secretary followed the process in
section 4672(a)(2)(B) in making this determination. A review of the stoichiometric
material consumption equation and other
information in the petition shows that the
taxable chemicals butylene, bromine, and
sodium hydroxide constitute more than
20 percent by weight of the materials
used in the production of bromo-isobutene-isoprene rubber ((C4H8)n-(C5H7.5Br0.5)
; n=98.20, m=1.80), based on the predomm
inant method of production. Therefore, the
test in section 4672(a)(2)(B) is satisfied.
(4) Date of determination: September
15, 2025.
(5) Effective dates for addition of bromo-isobutene-isoprene rubber ((C4H8)
-(C5H7.5Br0.5)m; n=98.20, m=1.80) to
n
the List:
(i) Effective date for purposes of the
section 4671 tax (see section 11.01 of Rev.
Proc. 2022-26): January 1, 2026

Bulletin No. 2025–41

(ii) Effective date for purposes of refund
claims under section 4662(e) (see sections
11.02 and 11.03 of Rev. Proc. 2022-26, as
modified by section 3 of Rev. Proc. 202320): April 1, 2023
(6) Tax rate prescribed by the Secretary: $9.72 per ton. The conversion factors for the taxable chemicals used in the
production of bromo-isobutene-isoprene
rubber ((C4H8)n-(C5H7.5Br0.5)m; n=98.20,
m=1.80) are 0.97 for butylene, 0.03 for
bromine, and 0.01 for sodium hydroxide.
The tax rate is calculated by adding the
products of the conversion factor for each
taxable chemical by the tax rate for that
taxable chemical: ((0.97 x $9.74) + (0.03
x $8.90) + (0.01 x $0.56) = $9.72).
(b) Classification numbers.
(1) The Secretary has no basis to object
to the following proposed classification
numbers:
(i) HTSUS number: 4002.39.0000
(ii) Schedule B number: 4002.39.0000
(iii) CAS number: 68441-14-5
(2) The Secretary is unable to confirm the following proposed classification
numbers: Not applicable.
3. Determination to Add Chloroprene
Rubber to the List
Arlanxeo USA LLC and Arlanxeo
Canada Inc., importers and exporters of
chloroprene rubber, submitted a petition
in accordance with Rev. Proc. 2022-26
requesting to add chloroprene rubber to
the List. According to the petition, the taxable chemicals butadiene, chlorine, and
sodium hydroxide constitute 100 percent
by weight of the materials used to produce
chloroprene rubber, based on the predominant method of production.
(a) Determination. Chloroprene rubber
is added to the list of taxable substances
under section 4672(a). Other pertinent
information is as follows:
(1) Predominant method of production:
The predominant method of producing
chloroprene rubber is through polymerization of chloroprene initiated by a radical
initiator in an emulsion process. Chloroprene monomer is made from butadiene
by first reacting it with chlorine in the gas
phase at ca 500 K to form 3,4-dichlorobut-1-ene and 1,4-dichlorobut-2-ene. The
former, on reaction with sodium hydroxide, yields chloroprene monomer.

Bulletin No. 2025–41

(2) Stoichiometric material consumption equation:
n [C4H6 (butadiene) + Cl2 (chlorine)
+ NaOH (sodium hydroxide)] →
(C4H5Cl)n (chloroprene rubber) + n
NaCl + n H2O
(3) Reasons for the determination:
The chloroprene rubber petition was filed
on February 7, 2025. The notice of filing
summarizing the petition and requesting
comments was published in the Federal
Register (90 FR 14691) on April 3, 2025.
The Treasury Department and the IRS
received no written comments in response
to the notice of filing. A public hearing
was neither requested nor held.
The Secretary followed the process
in section 4672(a)(2)(B) in making this
determination. A review of the stoichiometric material consumption equation
and other information in the petition
shows that the taxable chemicals butadiene, chlorine, and sodium hydroxide constitute more than 20 percent by weight of
the materials used in the production of
chloroprene rubber, based on the predominant method of production. Therefore, the test in section 4672(a)(2)(B) is
satisfied.
(4) Date of determination: September
15, 2025.
(5) Effective dates for addition of chloroprene rubber to the List:
(i) Effective date for purposes of the
section 4671 tax (see section 11.01 of Rev.
Proc. 2022-26): January 1, 2026
(ii) Effective date for purposes of refund
claims under section 4662(e) (see sections
11.02 and 11.03 of Rev. Proc. 2022-26, as
modified by section 3 of Rev. Proc. 202320): July 1, 2022
(6) Tax rate prescribed by the Secretary:
$10.51 per ton. The conversion factors for
the taxable chemicals used in the production
of chloroprene rubber are 0.61 for butadiene, 0.80 for chlorine, and 0.45 for sodium
hydroxide. The tax rate is calculated by
adding the products of the conversion factor for each taxable chemical by the tax rate
for that taxable chemical: ((0.61 x $9.74) +
(0.80 x $5.40) + (0.45 x $0.56) = $10.51).
(b) Classification numbers.
(1) The Secretary has no basis to object
to the following proposed classification
numbers:

451

(i) HTSUS number: 4002.49.0000
(ii) Schedule B number: 4002.49.0000
(iii) CAS number: 9010-98-4
(2) The Secretary is unable to confirm the following proposed classification
numbers:
(i) HTSUS number: 4002.99.0000
(ii) Schedule B number: 4002.99.0000
4. Determination to Add Ethylenepropylene-ethylidene Norbornene
Rubber ((C2H4)m-(C3H6)n(C9H12)o;
m=56.82, n=40.46, o=2.71) to the List
Arlanxeo USA LLC and Arlanxeo
Canada Inc., importers and exporters
of ethylene-propylene-ethylidene norbornene rubber ((C2H4)m-(C3H6)n(C9H12)
; m=56.82, n=40.46, o=2.71), submitted
o
a petition in accordance with Rev. Proc.
2022-26 requesting to add ethylene-propylene-ethylidene norbornene rubber ((C2H4)
-(C3H6)n(C9H12)o; m=56.82, n=40.46,
m
o=2.71) to the List. According to the petition, the taxable chemicals ethylene, propylene, and butadiene constitute 95.05
percent by weight of the materials used
to produce ethylene-propylene-ethylidene
norbornene rubber ((C2H4)m-(C3H6)n(C9H12)
; m=56.82, n=40.46, o=2.71), based on the
o
predominant method of production.
(a) Determination. Ethylene-propylene-ethylidene norbornene rubber ((C2H4)
-(C3H6)n(C9H12)o; m=56.82, n=40.46,
m
o=2.71) is added to the list of taxable substances under section 4672(a). Other pertinent information is as follows:
(1) Predominant method of production:
The predominant method of producing ethylene-propylene-ethylidene norbornene
rubber is through the catalytic polymerization of ethylene, propylene, and nonconjugated diene monomers in a solution
using various catalysts. Non-conjugated
diene monomers include ethylidene norbornene and dicyclopentadiene. The nonconjugated diene monomers are produced
from cyclopentadiene and butadiene, and
cyclopentadiene, respectively.
(2) Stoichiometric material consumption equation:
m C2H4 (ethylene) + n C3H6 (propylene) + o [C5H6 (cyclopentadiene) + C4H6 (butadiene)] → (C2H4)
-(C3H6)n(C9H12)o (ethylene-propylm
ene-ethylidene norbornene rubber)

October 6, 2025

(3) Reasons for the determination:
The ethylene-propylene-ethylidene norbornene rubber ((C2H4)m-(C3H6)n(C9H12)
; m=56.82, n=40.46, o=2.71) petition
o
was filed on February 7, 2025. The notice
of filing summarizing the petition and
requesting comments was published in
the Federal Register (90 FR 14695) on
April 3, 2025. The Treasury Department
and the IRS received no written comments in response to the notice of filing.
A public hearing was neither requested
nor held.
The Secretary followed the process
in section 4672(a)(2)(B) in making this
determination. A review of the stoichiometric material consumption equation and
other information in the petition shows
that the taxable chemicals ethylene, propylene, and butadiene constitute more
than 20 percent by weight of the materials
used in the production of ethylene-propylene-ethylidene norbornene rubber ((C2H4)
-(C3H6)n(C9H12)o; m=56.82, n=40.46,
m
o=2.71), based on the predominant
method of production. Therefore, the test
in section 4672(a)(2)(B) is satisfied.
(4) Date of determination: September
15, 2025.
(5) Effective dates for addition of
ethylene-propylene-ethylidene
norbornene rubber ((C2H4)m-(C3H6)n(C9H12)
; m=56.82, n=40.46, o=2.71) to the List:
o
(i) Effective date for purposes of the
section 4671 tax (see section 11.01 of Rev.
Proc. 2022-26): January 1, 2026
(ii) Effective date for purposes of refund
claims under section 4662(e) (see sections
11.02 and 11.03 of Rev. Proc. 2022-26, as
modified by section 3 of Rev. Proc. 202320): April 1, 2023
(6) Tax rate prescribed by the Secretary:
$9.25 per ton. The conversion factors for
the taxable chemicals used in the production of ethylene-propylene-ethylidene norbornene rubber ((C2H4)m-(C3H6)n(C9H12)
; m=56.82, n=40.46, o=2.71) are 0.44 for
o
ethylene, 0.47 for propylene, and 0.04 for
butadiene. The tax rate is calculated by
adding the products of the conversion factor for each taxable chemical by the tax rate
for that taxable chemical: ((0.44 x $9.74) +
(0.47 x $9.74) + (0.04 x $9.74) = $9.25).
(b) Classification numbers.
(1) The Secretary has no basis to object
to the following proposed classification
numbers:

October 6, 2025

(i) HTSUS number: 4002.70.0000
(ii) Schedule B number: 4002.70.0000
(iii) CAS number: 25038-36-2
(2) The Secretary is unable to confirm the following proposed classification
numbers: Not applicable.
5. Determination to Add Ethylene
Vinyl Acetate (VA < 50%) ((C2H4)
-(C4H6O2)m; n=78.95, m=21.05) to the
n
List
Arlanxeo USA LLC and Arlanxeo
Canada Inc., importers and exporters
of ethylene vinyl acetate (VA < 50%)
((C2H4)n-(C4H6O2)m; n=78.95, m=21.05),
submitted a petition in accordance with
Rev. Proc. 2022-26 requesting to add ethylene vinyl acetate (VA < 50%) ((C2H4)
-(C4H6O2)m; n=78.95, m=21.05) to the
n
List. According to the petition, the taxable chemicals ethylene and methane
constitute 66.23 percent by weight of the
materials used to produce ethylene vinyl
acetate (VA < 50%) ((C2H4)n-(C4H6O2)m;
n=78.95, m=21.05), based on the predominant method of production.
(a) Determination. Ethylene vinyl
acetate (VA < 50%) ((C2H4)n-(C4H6O2)m;
n=78.95, m=21.05) is added to the list of
taxable substances under section 4672(a).
Other pertinent information is as follows:
(1) Predominant method of production: The predominant method of producing ethylene vinyl acetate (VA < 50%)
((C2H4)n-(C4H6O2)m; n=78.95, m=21.05)
is through a solution polymerization
employing the monomers of ethylene and
vinyl acetate in tert-butanol as a solvent
and a radical polymerization initiator.
(2) Stoichiometric material consumption equation:
n C2H4 (ethylene) + m [C2H4 (ethylene) + 1/2 CH4 (methane) + 2 CO +
1/2 O2] → (C2H4)n(C4H6O2)m (ethylene
vinyl acetate (VA < 50%)) + 1/2m CO2
(3) Reasons for the determination: The
ethylene vinyl acetate (VA < 50%) ((C2H4)
-(C4H6O2)m; n=78.95, m=21.05) petin
tion was filed on February 7, 2025. The
notice of filing summarizing the petition
and requesting comments was published
in the Federal Register (90 FR 14688) on
April 3, 2025. The Treasury Department
and the IRS received no written comments

452

in response to the notice of filing. A public
hearing was neither requested nor held.
The Secretary followed the process
in section 4672(a)(2)(B) in making this
determination. A review of the stoichiometric material consumption equation
and other information in the petition
shows that the taxable chemicals ethylene and methane constitute more than
20 percent by weight of the materials
used in the production of, based on the
predominant method of production.
Therefore, the test in section 4672(a)(2)
(B) is satisfied.
(4) Date of determination: September
15, 2025.
(5) Effective dates for addition of ethylene vinyl acetate (VA < 50%) ((C2H4)
-(C4H6O2)m; n=78.95, m=21.05) to the
n
List:
(i) Effective date for purposes of the
section 4671 tax (see section 11.01 of Rev.
Proc. 2022-26): January 1, 2026
(ii) Effective date for purposes of refund
claims under section 4662(e) (see sections
11.02 and 11.03 of Rev. Proc. 2022-26, as
modified by section 3 of Rev. Proc. 202320): July 1, 2022
(6) Tax rate prescribed by the Secretary: $7.09 per ton. The conversion factors for the taxable chemicals used in the
production of ethylene vinyl acetate ((VA
< 50%) ((C2H4)n-(C4H6O2)m; n=78.95,
m=21.05) are 0.70 for ethylene and 0.04
for methane. The tax rate is calculated by
adding the products of the conversion factor for each taxable chemical by the tax
rate for that taxable chemical: ((0.70 x
$9.74) + (0.04 x $6.88) = $7.09).
(b) Classification numbers.
(1) The Secretary has no basis to object
to the following proposed classification
numbers:
(i) HTSUS number: 3901.30.6000
(ii) Schedule B number: 3901.30.6000
(iii) CAS number: 24937-78-8
(2) The Secretary is unable to confirm the following proposed classification
numbers: Not applicable.
6. Determination to Add Ethylene
Vinyl Acetate (VA ≥ 50%) ((C2H4)
-(C4H6O2)m; n=75.42, m=24.58) to the
n
List
Arlanxeo USA LLC and Arlanxeo
Canada Inc., importers and exporters

Bulletin No. 2025–41

of ethylene vinyl acetate (VA ≥ 50%)
((C2H4)n-(C4H6O2)m; n=75.42, m=24.58),
submitted a petition in accordance with
Rev. Proc. 2022-26 requesting to add ethylene vinyl acetate (VA ≥ 50%) ((C2H4)
-(C4H6O2)m; n=75.42, m=24.58) to the
n
List. According to the petition, the taxable chemicals ethylene and methane
constitute 62.91 percent by weight of the
materials used to produce ethylene vinyl
acetate (VA ≥ 50%) ((C2H4)n-(C4H6O2)m;
n=75.42, m=24.58), based on the predominant method of production.
(a) Determination. Ethylene vinyl
acetate (VA ≥ 50%) ((C2H4)n-(C4H6O2)m;
n=75.42, m=24.58) is added to the list of
taxable substances under section 4672(a).
Other pertinent information is as follows:
(1) Predominant method of production: The predominant method of producing ethylene vinyl acetate (VA ≥ 50%)
((C2H4)n-(C4H6O2)m; n=75.42, m=24.58)
is through a solution polymerization
employing the monomers of ethylene and
vinyl acetate in tert-butanol as a solvent
and a radical polymerization initiator.
(2) Stoichiometric material consumption equation:
n C2H4 (ethylene) + m [C2H4 (ethylene) + 1/2 CH4 (methane) + 2 CO +
1/2 O2] → (C2H4)n(C4H6O2)m (ethylene
vinyl acetate (VA ≥ 50%)) + 1/2m CO2
(3) Reasons for the determination:
The ethylene vinyl acetate (VA ≥ 50%)
((C2H4)n-(C4H6O2)m; n=75.42, m=24.58)
petition was filed on February 7, 2025.
The notice of filing summarizing the
petition and requesting comments was
published in the Federal Register (90
FR 14683) on April 3, 2025. The Treasury Department and the IRS received
no written comments in response to the
notice of filing. A public hearing was neither requested nor held.
The Secretary followed the process
in section 4672(a)(2)(B) in making this
determination. A review of the stoichiometric material consumption equation and
other information in the petition shows
that the taxable chemicals ethylene and
methane constitute more than 20 percent
by weight of the materials used in the
production of, based on the predominant
method of production. Therefore, the test
in section 4672(a)(2)(B) is satisfied.

Bulletin No. 2025–41

(4) Date of determination: September
15, 2025.
(5) Effective dates for addition of ethylene vinyl acetate (VA ≥ 50%) ((C2H4)
-(C4H6O2)m; n=75.42, m=24.58) to the List:
n
(i) Effective date for purposes of the
section 4671 tax (see section 11.01 of Rev.
Proc. 2022-26): January 1, 2026
(ii) Effective date for purposes of refund
claims under section 4662(e) (see sections
11.02 and 11.03 of Rev. Proc. 2022-26, as
modified by section 3 of Rev. Proc. 202320): July 1, 2022
(6) Tax rate prescribed by the Secretary: $6.77 per ton. The conversion factors for the taxable chemicals used in the
production of ethylene vinyl acetate (VA
≥ 50%) ((C2H4)n-(C4H6O2)m; n=75.42,
m=24.58) are 0.66 for ethylene and 0.05
for methane. The tax rate is calculated by
adding the products of the conversion factor for each taxable chemical by the tax
rate for that taxable chemical: ((0.66 x
$9.74) + (0.05 x $6.88) = $6.77).
(b) Classification numbers.
(1) The Secretary has no basis to object
to the following proposed classification
numbers:
(i) HTSUS number: 3905.29.0000
(ii) Schedule B number: 3905.29.0000
(iii) CAS number: 24937-78-8
(2) The Secretary is unable to confirm
the following classification numbers: Not
applicable.
7. Determination to Add Hydrogenated
Acrylonitrile-Butadiene Rubber
((C4H8)n-(C3H3N)m; n=22.28, m=38.86)
to the List
Arlanxeo USA LLC and Arlanxeo
Canada Inc., importers and exporters
of hydrogenated acrylonitrile-butadiene rubber ((C4H8)n-(C3H3N)m; n=22.28,
m=38.86), submitted a petition in
accordance with Rev. Proc. 2022-26
requesting to add hydrogenated acrylonitrile-butadiene
rubber
((C4H8)
-(C
H
N)
;
n=22.28,
m=38.86)
to the
n
3 3
m
List. According to the petition, the
taxable chemicals butadiene, propylene, ammonia, and methane constitute
63.48 percent by weight of the materials
used to produce hydrogenated acrylonitrile-butadiene rubber ((C4H8)n-(C3H3N)
; n=22.28, m=38.86), based on the prem
dominant method of production.

453

(a) Determination. Hydrogenated
acrylonitrile-butadiene rubber ((C4H8)
-(C3H3N)m; n=22.28, m=38.86) is added
n
to the list of taxable substances under section 4672(a). Other pertinent information
is as follows:
(1) Predominant method of production: The predominant method of producing hydrogenated acrylonitrile-butadiene
rubber is via catalytic hydrogenation of
acrylonitrile-butadiene rubber which is
derived from the emulsion polymerization
of butadiene and acrylonitrile.
(2) Stoichiometric material consumption equation:
n C4H6 (butadiene) + m [C3H6 (propylene) + NH3 (ammonia) + 3/2 O2]
+ n [1/4 CH4 (methane) + 1/2 H2O]
→ (C4H8)n-(C3H3N)m (hydrogenated
acrylonitrile-butadiene rubber) + 3m
H2O + 1/4n CO2
(3) Reasons for the determination:
The hydrogenated acrylonitrile-butadiene rubber (C4H8)n-(C3H3N)m; n=22.28,
m=38.86) petition was filed on February
7, 2025. The notice of filing summarizing the petition and requesting comments
was published in the Federal Register (90
FR 14686) on April 3, 2025. The Treasury Department and the IRS received
two non-substantive written comments in
response to the notice of filing. One comment received by the IRS recommended
prohibiting the manufacture of this substance. The other comment received by
the IRS was unrelated to the determination for this substance. The comments
did not address whether hydrogenated
acrylonitrile-butadiene rubber ((C4H8)
-(C3H3N)m; n=22.28, m=38.86) meets
n
the weight or value test under section
4672(a)(2)(B). A public hearing was neither requested nor held.
The Secretary followed the process
in section 4672(a)(2)(B) in making this
determination. A review of the stoichiometric material consumption equation and
other information in the petition shows
that the taxable chemicals butadiene, propylene, ammonia, and methane constitute
more than 20 percent by weight of the
materials used in the production of, based
on the predominant method of production.
Therefore, the test in section 4672(a)(2)
(B) is satisfied.

October 6, 2025

(4) Date of determination: September
15, 2025.
(5) Effective dates for addition of
hydrogenated
acrylonitrile-butadiene
rubber
(C4H8)n-(C3H3N)m;
n=22.28,
m=38.86) to the List:
(i) Effective date for purposes of the
section 4671 tax (see section 11.01 of Rev.
Proc. 2022-26): January 1, 2026
(ii) Effective date for purposes of refund
claims under section 4662(e) (see sections
11.02 and 11.03 of Rev. Proc. 2022-26, as
modified by section 3 of Rev. Proc. 202320): July 1, 2022
(6) Tax rate prescribed by the Secretary: $9.54 per ton. The conversion
factors for the taxable chemicals used
in the production of hydrogenated
acrylonitrile-butadiene rubber (C4H8)
-(C3H3N)m; n=22.28, m=38.86) are 0.36
n
for butadiene, 0.49 for propylene, 0.20
for ammonia, and 0.03 for methane.
The tax rate is calculated by adding the
products of the conversion factor for
each taxable chemical by the tax rate for
that taxable chemical: ((0.36 x $9.74) +
(0.49 x $9.74) + (0.20 x $5.28) + (0.03 x
$6.88) = $9.54).
(b) Classification numbers.
(1) The Secretary has no basis to object
to the following proposed classification
numbers:
(i) HTSUS number: 4002.59.0000
(ii) Schedule B number: 4002.59.0000
(iii) CAS number: 308068-83-9
(2) The Secretary is unable to confirm
the following classification numbers: Not
applicable.
8. Determination To Add Isobuteneisoprene Rubber ((C4H8)n-(C5H8)m;
n=99.10, m=0.90) to the List
Arlanxeo USA LLC and Arlanxeo
Canada Inc., importers and exporters of
isobutene-isoprene rubber ((C4H8)n-(C5H8)
; n=99.10, m=0.90) submitted a petition
m
in accordance with Rev. Proc. 2022-26
requesting to add isobutene-isoprene rubber ((C4H8)n-(C5H8)m; n=99.10, m=0.90)
to the List. According to the petition, the
taxable chemical butylene constitutes
98.91 percent by weight of the materials
used to produce isobutene-isoprene rubber ((C4H8)n-(C5H8)m; n=99.10, m=0.90),
based on the predominant method of production.

October 6, 2025

(a) Determination. Isobutene-isoprene rubber ((C4H8)n-(C5H8)m; n=99.10,
m=0.90) is added to the list of taxable
substances under section 4672(a). Other
pertinent information is as follows:
(1) Predominant method of production: The predominant method of producing isobutene-isoprene rubber is via
the cationic copolymerization of butylene
with isoprene in the presence of a Friedel-Crafts catalyst at low temperature,
around -100°C. The final product contains
0.7 wt% of additives.
(2) Stoichiometric material consumption equation:
n C4H8 (butylene) + m C5H8 (isoprene)
→ (C4H8)n(C5H8)m (isobutene-isoprene
rubber)
(3) Reasons for the determination:
The isobutene-isoprene rubber ((C4H8)
-(C5H8)m; n=99.10, m=0.90) petition
n
was filed on February 7, 2025. The notice
of filing summarizing the petition and
requesting comments was published in
the Federal Register (90 FR 14689) on
April 3, 2025. The Treasury Department
and the IRS received no written comments in response to the notice of filing.
A public hearing was neither requested
nor held.
The Secretary followed the process in
section 4672(a)(2)(B) in making this determination. A review of the stoichiometric
material consumption equation and other
information in the petition shows that the
taxable chemical butylene constitutes more
than 20 percent by weight of the materials
used in the production of isobutene-isoprene rubber ((C4H8)n-(C5H8)m; n=99.10,
m=0.90), based on the predominant method
of production. Therefore, the test in section
4672(a)(2)(B) is satisfied.
(4) Date of determination: September
15, 2025.
(5) Effective dates for addition of isobutene-isoprene rubber ((C4H8)n-(C5H8)m;
n=99.10, m=0.90) to the List:
(i) Effective date for purposes of the
section 4671 tax (see section 11.01 of Rev.
Proc. 2022-26): January 1, 2026
(ii) Effective date for purposes of refund
claims under section 4662(e) (see sections
11.02 and 11.03 of Rev. Proc. 2022-26, as
modified by section 3 of Rev. Proc. 202320): July 1, 2022

454

(6) Tax rate prescribed by the Secretary: $9.64 per ton. The conversion factor
for the butylene used in the production of
isobutene-isoprene rubber ((C4H8)n-(C5H8)
; n=99.10, m=0.90) is 0.99. The tax rate
m
is calculated by multiplying the conversion factor by the tax rate for butylene:
(0.99 x $9.74 = $9.64).
(b) Classification numbers.
(1) The Secretary has no basis to object
to the following proposed classification
numbers:
(i) HTSUS number: 4002.31.0000
(ii) Schedule B number: 4002.31.0000
(iii) CAS number: 9010-85-9
(2) The Secretary is unable to confirm the following proposed classification
numbers: Not applicable.
9. Determination to Add Poly(ethylenepropylene) Rubber ((C2H4)m-(C3H6)n;
m=59.04, n=40.96) to the List
Arlanxeo USA LLC and Arlanxeo
Canada Inc., importers and exporters of
poly(ethylene-propylene) rubber ((C2H4)
-(C3H6)n; m=59.04, n=40.96), submitm
ted a petition in accordance with Rev.
Proc. 2022-26 requesting to add poly(ethylene-propylene) rubber ((C2H4)m-(C3H6)n;
m=59.04, n=40.96) to the List. According
to the petition, the taxable chemicals ethylene and propylene constitute 100 percent
by weight of the materials used to produce
poly(ethylene-propylene) rubber ((C2H4)
-(C3H6)n; m=59.04, n=40.96), based on
m
the predominant method of production.
(a) Determination. Poly(ethylene-propylene)
rubber
((C2H4)m-(C3H6)n;
m=59.04, n=40.96) is added to the list of
taxable substances under section 4672(a).
Other pertinent information is as follows:
(1) Predominant method of production: The predominant method of producing poly(ethylene-propylene) rubber
is through the catalytic polymerization
of ethylene and propylene monomers in a
solution using various catalysts.
(2) Stoichiometric material consumption equation:
m C2H4 (ethylene) + n C3H6 (propylene) → (C2H4)m-(C3H6)n (poly(ethylene-propylene) rubber)
(3) Reasons for the determination: The
poly(ethylene-propylene) rubber ((C2H4)

Bulletin No. 2025–41

-(C3H6)n; m=59.04, n=40.96) petition
was filed on February 7, 2025. The notice
of filing summarizing the petition and
requesting comments was published in
the Federal Register (90 FR 14690) on
April 3, 2025. The Treasury Department
and the IRS received no written comments in response to the notice of filing.
A public hearing was neither requested
nor held.
The Secretary followed the process
in section 4672(a)(2)(B) in making this
determination. A review of the stoichiometric material consumption equation and
other information in the petition shows
that the taxable chemicals ethylene and
propylene constitute more than 20 percent
by weight of the materials used in the production of poly(ethylene-propylene) rubber ((C2H4)m-(C3H6)n; m=59.04, n=40.96),
based on the predominant method of
production. Therefore, the test in section
4672(a)(2)(B) is satisfied.
(4) Date of determination: September
15, 2025.
(5) Effective dates for addition of
poly(ethylene-propylene) rubber ((C2H4)
-(C3H6)n; m=59.04, n=40.96) to the List:
m
(i) Effective date for purposes of the
section 4671 tax (see section 11.01 of Rev.
Proc. 2022-26): January 1, 2026
(ii) Effective date for purposes of refund
claims under section 4662(e) (see sections
11.02 and 11.03 of Rev. Proc. 2022-26, as
modified by section 3 of Rev. Proc. 202320): July 1, 2022
(6) Tax rate prescribed by the Secretary: $9.74 per ton. The conversion
factors for the taxable chemicals used in
the production of poly(ethylene-propylene) rubber ((C2H4)m-(C3H6)n; m=59.04,
n=40.96) are 0.49 for ethylene and 0.51
for propylene. The tax rate is calculated
by adding the products of the conversion factor for each taxable chemical
and the tax rate for that taxable chemical: ((0.49 x $9.74) + (0.51 x $9.74) =
$9.74).
(b) Classification numbers.
(1) The Secretary has no basis to object
to the following proposed classification
number: CAS number: 9010-71-1
(2) The Secretary is unable to confirm the following proposed classification
numbers:
(i) HTSUS number: 3901.40.0000
(ii) Schedule B number: 3901.40.0000
m

Bulletin No. 2025–41

10. Determination to Add Emulsion
Styrene-butadiene Rubber ((C4H6)
-(C8H8)n; m=15.83, n=2.53) to the List
m
Arlanxeo USA LLC and Arlanxeo
Canada Inc., importers and exporters
of emulsion styrene-butadiene rubber
((C4H6)m-(C8H8)n; m=15.83; n=2.53), submitted a petition in accordance with Rev.
Proc. 2022-26 requesting to add emulsion
styrene-butadiene rubber ((C4H6)m-(C8H8)
; m=15.83; n=2.53) to the List. Accordn
ing to the petition, the taxable chemicals
butadiene, benzene, and ethylene constitute 100 percent by weight of the materials
used to produce emulsion styrene-butadiene rubber ((C4H6)m-(C8H8)n; m=15.83;
n=2.53), based on the predominant
method of production.
(a) Determination. Emulsion styrene-butadiene rubber ((C4H6)m-(C8H8)n;
m=15.83; n=2.53) is added to the list of
taxable substances under section 4672(a).
Other pertinent information is as follows:
(1) Predominant method of production: The predominant method of producing emulsion styrene-butadiene rubber is
through the emulsion polymerization of
butadiene and styrene initiated by free
radicals. Styrene monomer is produced by
the dehydrogenation of ethylbenzene. Ethylbenzene is produced via a Friedel-Crafts
reaction of benzene and ethylene.
(2) Stoichiometric material consumption equation:
m C4H6 (butadiene) + n [C6H6 (benzene) + C2H4 (ethylene)] → (C4H6)
-(C8H8)n (emulsion styrene-butadiene
m
rubber) + n H2 (hydrogen)
(3) Reasons for the determination:
The emulsion styrene-butadiene rubber
((C4H6)m-(C8H8)n; m=15.83; n=2.53) petition was filed on February 7, 2025. The
notice of filing summarizing the petition
and requesting comments was published
in the Federal Register (90 FR 14686) on
April 3, 2025. The Treasury Department
and the IRS received no written comments
in response to the notice of filing. A public
hearing was neither requested nor held.
The Secretary followed the process
in section 4672(a)(2)(B) in making this
determination. A review of the stoichiometric material consumption equation
and other information in the petition

455

shows that the taxable chemicals butadiene, benzene, and ethylene constitute
more than 20 percent by weight of the
materials used in the production of emulsion styrene-butadiene rubber ((C4H6)
-(C8H8)n; m=15.83; n=2.53), based on
m
the predominant method of production.
Therefore, the test in section 4672(a)(2)
(B) is satisfied.
(4) Date of determination: September
15, 2025.
(5) Effective dates for addition of emulsion styrene-butadiene rubber ((C4H6)
-(C8H8)n; m=15.83; n=2.53) to the List:
m
(i) Effective date for purposes of the
section 4671 tax (see section 11.01 of Rev.
Proc. 2022-26): January 1, 2026
(ii) Effective date for purposes of refund
claims under section 4662(e) (see sections
11.02 and 11.03 of Rev. Proc. 2022-26, as
modified by section 3 of Rev. Proc. 202320): July 1, 2022
(6) Tax rate prescribed by the Secretary: $9.74 per ton. The conversion factors for the taxable chemicals used in the
production of emulsion styrene-butadiene rubber ((C4H6)m-(C8H8)n; m=15.83;
n=2.53) are 0.76 for butadiene, 0.18 for
benzene, and 0.06 for ethylene. The tax
rate is calculated by adding the products
of the conversion factor for each taxable
chemical and the tax rate for that taxable
chemical: ((0.76 x $9.74) + (0.18 x $9.74)
+ (0.06 x $9.74) = $9.74).
(b) Classification numbers.
(1) The Secretary has no basis to object
to the following proposed classification
numbers:
(i) HTSUS numbers: 4002.19.0015
(rubber), 4002.11.0000 (latex)
(ii) Schedule B numbers: 4002.19.9000
(rubber), 4002.11.0000 (latex)
(iii) CAS number: 9003-55-8
(2) The Secretary is unable to confirm the following proposed classification
numbers: Not applicable.
11. Determination to Add Solution
Styrene-butadiene Rubber ((C4H6)
-(C8H8)n; m=67.16, n=32.85) to the
m
List
Arlanxeo USA LLC and Arlanxeo
Canada Inc., importers and exporters of
solution styrene-butadiene rubber ((C4H6)
-(C8H8)n; m=67.16; n=32.85), submitted
m
a petition in accordance with Rev. Proc.

October 6, 2025

2022-26 requesting to add solution styrene-butadiene rubber ((C4H6)m-(C8H8)n;
m=67.16; n=32.85) to the List. According to the petition, the taxable chemicals
butadiene, benzene, and ethylene constitute 100 percent by weight of the materials used to produce solution styrene-butadiene rubber ((C4H6)m-(C8H8)n; m=67.16;
n=32.85), based on the predominant
method of production.
(a) Determination. Solution styrene-butadiene rubber ((C4H6)m-(C8H8)n;
m=67.16; n=32.85) is added to the list of
taxable substances under section 4672(a).
Other pertinent information is as follows:
(1) Predominant method of production: The predominant method of
producing solution styrene-butadiene
rubber is through the anionic polymerization of butadiene and styrene initiated by alkyl lithium compounds in
hexanes as solvent. Styrene monomer
is produced by the dehydrogenation of
ethylbenzene. Ethylbenzene is produced
via a Friedel-Crafts reaction of benzene
and ethylene.
(2) Stoichiometric material consumption equation:
m C4H6 (butadiene) + n [C6H6 (benzene) + C2H4 (ethylene)] → (C4H6)
-(C8H8)n (solution styrene-butadiene
m
rubber) + n H2 (hydrogen); m=67.16;
n=32.85
(3) Reasons for the determination:
The solution styrene-butadiene rubber
((C4H6)m-(C8H8)n; m=67.16; n=32.85)
petition was filed on February 7, 2025.
The notice of filing summarizing the
petition and requesting comments was
published in the Federal Register (90
FR 14690) on April 3, 2025. The Treasury Department and the IRS received
no written comments in response to the
notice of filing. A public hearing was neither requested nor held.
The Secretary followed the process
in section 4672(a)(2)(B) in making this
determination. A review of the stoichiometric material consumption equation and
other information in the petition shows
that the taxable chemicals butadiene, benzene, and ethylene constitute more than 20
percent by weight of the materials used in
the production of solution styrene-butadiene rubber ((C4H6)m-(C8H8)n; m=67.16;

October 6, 2025

n=32.85), based on the predominant
method of production. Therefore, the test
in section 4672(a)(2)(B) is satisfied.
(4) Date of determination: September
15, 2025.
(5) Effective dates for addition of solution styrene-butadiene rubber ((C4H6)
-(C8H8)n; m=67.16; n=32.85) to the List:
m
(i) Effective date for purposes of the
section 4671 tax (see section 11.01 of Rev.
Proc. 2022-26): January 1, 2026
(ii) Effective date for purposes of refund
claims under section 4662(e) (see sections
11.02 and 11.03 of Rev. Proc. 2022-26, as
modified by section 3 of Rev. Proc. 202320): July 1, 2022
(6) Tax rate prescribed by the Secretary: $9.74 per ton. The conversion factors
for the taxable chemicals used in the production of solution styrene-butadiene rubber ((C4H6)m-(C8H8)n; m=67.16; n=32.85)
are 0.51 for butadiene, 0.36 for benzene,
and 0.13 for ethylene. The tax rate is calculated by adding the products of the conversion factor for each taxable chemical
and the tax rate for that taxable chemical:
((0.51 x $9.74) + (0.36 x $9.74) + (0.13 x
$9.74) = $9.74).
(b) Classification numbers.
(1) The Secretary has no basis to object
to the following proposed classification
number: CAS number: 9003-55-8
(2) The Secretary is unable to confirm the following proposed classification
numbers:
(i) HTSUS number: 4002.19.0016
(ii) Schedule B number: 4002.19.1600
12. Determination to Add Emulsion
Styrene Butadiene Rubber ((C4H6)
-(C8H8)n; m=14.14, n=2.26) to the List
m
Michelin North America, Inc., an
importer of emulsion styrene butadiene rubber ((C4H6)m-(C8H8)n; m=14.14,
n=2.26), submitted a petition in accordance with Rev. Proc. 2022-26 requesting to add emulsion styrene butadiene
rubber
((C4H6)m-(C8H8)n;
m=14.14,
n=2.26) to the List. According to the
petition, the taxable chemicals butadiene,
benzene, and ethylene constitute 100 percent by weight of the materials used to
produce emulsion styrene butadiene rubber ((C4H6)m-(C8H8)n; m=14.14, n=2.26),
based on the predominant method of production.

456

(a) Determination. Emulsion styrene butadiene rubber ((C4H6)m-(C8H8)n;
m=14.14, n=2.26) is added to the list of
taxable substances under section 4672(a).
Other pertinent information is as follows:
(1) Predominant method of production:
The predominant method of producing
emulsion styrene butadiene rubber ((C4H6)
-(C8H8)n; m=14.14, n=2.26) is through a
m
low temperature, emulsion copolymerization of butadiene and styrene, using
fatty and rosin acid soaps as an emulsifier,
and organic hydroperoxides as an initiator. Styrene monomer is produced by the
dehydrogenation of ethylbenzene. Ethylbenzene is produced via a Friedel-Crafts
reaction of benzene and ethylene.
(2) Stoichiometric material consumption equation:
m C4H6 (butadiene) + n [C6H6 (benzene) + C2H4 (ethylene)] → (C4H6)
-(C8H8)n (emulsion styrene butadiene
m
rubber) + n H2 (hydrogen); m=14.14;
n=2.26
(3) Reasons for the determination:
The emulsion styrene butadiene rubber
((C4H6)m-(C8H8)n; m=14.14, n=2.26) petition was filed on February 7, 2025. The
notice of filing summarizing the petition
and requesting comments was published
in the Federal Register (90 FR 14692) on
April 3, 2025. The Treasury Department
and the IRS received no written comments in response to the notice of filing.
A public hearing was neither requested
nor held.
The Secretary followed the process
in section 4672(a)(2)(B) in making this
determination. A review of the stoichiometric material consumption equation
and other information in the petition
shows that the taxable chemicals butadiene, benzene, and ethylene constitute
more than 20 percent by weight of the
materials used in the production of emulsion styrene butadiene rubber ((C4H6)
-(C8H8)n; m=14.14, n=2.26), based on
m
the predominant method of production.
Therefore, the test in section 4672(a)(2)
(B) is satisfied.
(4) Date of determination: September
15, 2025.
(5) Effective dates for addition of emulsion styrene butadiene rubber ((C4H6)
-(C8H8)n; m=14.14, n=2.26) to the List:
m

Bulletin No. 2025–41

(i) Effective date for purposes of the
section 4671 tax (see section 11.01 of Rev.
Proc. 2022-26): January 1, 2026
(ii) Effective date for purposes of refund
claims under section 4662(e) (see sections
11.02 and 11.03 of Rev. Proc. 2022-26, as
modified by section 3 of Rev. Proc. 202320): July 1, 2022
(6) Tax rate prescribed by the Secretary: $9.74 per ton. The conversion factors for the taxable chemicals used in the
production of emulsion styrene butadiene rubber ((C4H6)m-(C8H8)n; m=14.14,
n=2.26) are 0.76 for butadiene, 0.18 for
benzene, and 0.06 for ethylene. The tax
rate is calculated by adding the products
of the conversion factor for each taxable
chemical and the tax rate for that taxable
chemical: ((0.76 x $9.74) + (0.18 x $9.74)
+ (0.06 x $9.74) = $9.74).
(b) Classification numbers.
(1) The Secretary has no basis to object
to the following proposed classification
numbers:
(i) HTSUS number: 4002.19.0015
(ii) Schedule B number: 4002.19.9000
(iii) CAS number: 9003-55-8
(2) The Secretary is unable to confirm the following proposed classification
numbers: Not applicable.
13. Determination to Add Solution
Styrene-butadiene Rubber ((C4H6)
-(C8H8)n; m=13.31, n=2.50) to the List
m
Michelin North America, Inc., an
importer of solution styrene-butadiene rubber ((C4H6)m-(C8H8)n; m=13.31,
n=2.50), submitted a petition in accordance with Rev. Proc. 2022-26 requesting
to add solution styrene-butadiene rubber
((C4H6)m-(C8H8)n; m=13.31, n=2.50) to
the List. According to the petition, the
taxable chemicals butadiene, benzene and
ethylene constitute 100 percent by weight
of the materials used to produce solution
styrene-butadiene rubber ((C4H6)m-(C8H8)
; m=13.31, n=2.50), based on the pren
dominant method of production.
(a) Determination. Solution styrene-butadiene rubber ((C4H6)m-(C8H8)n;
m=13.31, n=2.50) is added to the list of
taxable substances under section 4672(a).
Other pertinent information is as follows:
(1) Predominant method of production:
The predominant method of producing
solution styrene-butadiene rubber ((C4H6)

Bulletin No. 2025–41

-(C8H8)n; m=13.31, n=2.50) is through
the continuous polymerization of butadiene and styrene initiated by alkyl lithium
compounds in toluene or CMHC (cyclohexane and methylhexane) as solvents.
Styrene monomer is produced by the
dehydrogenation of ethylbenzene. Ethylbenzene is produced via a Friedel-Crafts
reaction of benzene and ethylene.
(2) Stoichiometric material consumption equation:

m

m C4H6 (butadiene) + n [C6H6 (benzene) + C2H4 (ethylene)] → (C4H6)
-(C8H8)n (solution styrene butadiene
m
rubber) + n H2 (hydrogen); m=13.31;
n=2.5
(3) Reasons for the determination:
The solution styrene-butadiene rubber
((C4H6)m-(C8H8)n; m=13.31, n=2.50) petition was filed on February 7, 2025. The
notice of filing summarizing the petition
and requesting comments was published
in the Federal Register (90 FR 14693) on
April 3, 2025. The Treasury Department
and the IRS received one non-substantive
written comment on the necessity of the
filing to understand its impact in response
to the notice of filing. The comment did
not address whether solution styrene-butadiene rubber ((C4H6)m-(C8H8)n; m=13.31,
n=2.50) meets the weight or value test
under section 4672(a)(2)(B). A public
hearing was neither requested nor held.
The Secretary followed the process
in section 4672(a)(2)(B) in making this
determination. A review of the stoichiometric material consumption equation
and other information in the petition
shows that the taxable chemicals butadiene, benzene and ethylene constitute
more than 20 percent by weight of the
materials used in the production of solution styrene-butadiene rubber ((C4H6)
-(C8H8)n; m=13.31, n=2.50), based on
m
the predominant method of production.
Therefore, the test in section 4672(a)(2)
(B) is satisfied.
(4) Date of determination: September
15, 2025.
(5) Effective dates for addition of solution styrene-butadiene rubber ((C4H6)
-(C8H8)n; m=13.31, n=2.50) to the List:
m
(i) Effective date for purposes of the
section 4671 tax (see section 11.01 of Rev.
Proc. 2022-26): January 1, 2026

457

(ii) Effective date for purposes of refund
claims under section 4662(e) (see sections
11.02 and 11.03 of Rev. Proc. 2022-26, as
modified by section 3 of Rev. Proc. 202320): July 1, 2022
(6) Tax rate prescribed by the Secretary: $9.74 per ton. The conversion factors
for the taxable chemicals used in the production of solution styrene-butadiene rubber ((C4H6)m-(C8H8)n; m=13.31, n=2.50)
are 0.73 for butylene, 0.20 for benzene,
and 0.07 for ethylene. The tax rate is calculated by adding the products of the conversion factor for each taxable chemical
and the tax rate for that taxable chemical:
((0.73 x $9.74) + (0.20 x $9.74) + (0.07 x
$9.74) = $9.74).
(b) Classification numbers.
(1) The Secretary has no basis to object
to the following proposed classification
numbers:
(i) HTSUS number: 4002.19.0016
(ii) Schedule B number: 4002.19.1600
(iii) CAS number: 9003-55-8
(2) The Secretary is unable to confirm the following proposed classification
numbers: Not applicable.
14. Determination to Add
Hydrogenated Acrylonitrile-butadiene
Rubber ((C4H8)x-(C3H3N)y-(C15H24O)a;
x=2,783.05, y=1,907.27, a=5.74) to the
List
Zeon Chemicals L.P., an importer
and exporter of hydrogenated acrylonitrile-butadiene rubber ((C4H8)x-(C3H3N)
-(C15H24O)a; x=2,783.05, y=1,907.27,
y
a=5.74), also known as “HNBR,” submitted a petition in accordance with Rev.
Proc. 2022-26 requesting to add HNBR
to the List. According to the petition, the
taxable chemicals butadiene, propylene,
ammonia, methane, butylene, toluene, sulfuric acid, and sodium hydroxide constitute 67.01 percent by weight of the materials used to produce HNBR, based on the
predominant method of production.
(a) Determination. Hydrogenated
acrylonitrile-butadiene rubber ((C4H8)
-(C3H3N)y-(C15H24O)a;
x=2,783.05,
x
y=1,907.27, a=5.74) is added to the list of
taxable substances under section 4672(a).
Other pertinent information is as follows:
(1) Predominant method of production:
The predominant method of producing
HNBR is via catalytic hydrogenation of

October 6, 2025

acrylonitrile-butadiene rubber (“NBR”)
in a solution of acetone and in the presence of a catalyst. NBR is derived from
the emulsion polymerization of butadiene
and acrylonitrile. Acrylonitrile monomer
is produced by the SOHIO process (i.e.,
catalytic ammoxidation of propylene).
Hydrogen is made from steam-methane
reforming. Butylated hydroxytoluene is
produced from the reaction of p-cresol
with butylene. p-Cresol is prepared by a
two-step route beginning with the sulfonation of toluene, followed by basic hydrolysis.
(2) Stoichiometric material consumption equation:
x C4H6 (butadiene) + y C3H6 (propylene) + y NH3 (ammonia) + 3/2y O2 +
1/2x CH4 (methane) + x H2O + a C7H8
(toluene) + a H2SO4 (sulfuric acid) +
2a NaOH (sodium hydroxide) + 2a
C4H8 (butylene) → (C4H8)x-(C3H3N)
-(C15H24O)a (HNBR) + 1/2x CO2 (cary
bon dioxide)+ (3y+2a) H2O (water)
+ a Na2SO3 (sodium sulfite)+ x H21
(hydrogen)
(3) Reasons for the determination: The
HNBR petition was filed on February 14,
2025. The notice of filing summarizing
the petition and requesting comments was
published in the Federal Register (90 FR
14685) on April 3, 2025, and a correction
was published in the Federal Register (90
FR 19245) on May 6, 2025. The Treasury
Department and the IRS received no written comments in response to the notice
of filing. A public hearing was neither
requested nor held.
The Secretary followed the process
in section 4672(a)(2)(B) in making this
determination. A review of the stoichiometric material consumption equation
and other information in the petition
shows that the taxable chemicals butadiene, propylene, ammonia, methane, butylene, toluene, sulfuric acid, and sodium
hydroxide constitute more than 20 percent by weight of the materials used in
the production of HNBR, based on the
predominant method of production.

Therefore, the test in section 4672(a)(2)
(B) is satisfied.
(4) Date of determination: September
15, 2025.
(5) Effective dates for addition of
HNBR to the List:
(i) Effective date for purposes of the
section 4671 tax (see section 11.01 of Rev.
Proc. 2022-26): January 1, 2026
(ii) Effective date for purposes of refund
claims under section 4662(e) (see sections
11.02 and 11.03 of Rev. Proc. 2022-26, as
modified by section 3 of Rev. Proc. 202320): April 1, 2023
(6) Tax rate prescribed by the Secretary: $10.02 per ton. The conversion factors for the taxable chemicals used in the
production of HNBR are 0.58 for butadiene, 0.31 for propylene, 0.13 for ammonia, 0.09 for methane, 0.002 for butylene,
0.002 for toluene, 0.002 for sulfuric acid,
and 0.002 for sodium hydroxide. The tax
rate is calculated by adding the products
of the conversion factor for each taxable
chemical and the tax rate for that taxable
chemical: ((0.58 x $9.74) + (0.31 x $9.74)
+ (0.13 x $5.28) + (0.09 x $6.88) + (0.002
x $9.74) + (0.002 x $9.74) + (0.002 x
$0.52) + (0.002 x $0.56) = $10.02).
(b) Classification numbers.
(1) The Secretary has no basis to object
to the following proposed classification
numbers:
(i) HTSUS number: 4002.59.00002
(ii) Schedule B number: 4002.59.0000
(iii) CAS number: 88254-10-8
(2) The Secretary is unable to confirm the following proposed classification
numbers: Not applicable.
15. Determination to Add Bromobutyl
Isobutylene Isoprene Rubber (((C4H8)
(C5H8)y(Br2)z); x=7071, y=59, z=50) to
x
the List
Exxon Mobil Corporation, an exporter
of bromobutyl isobutylene isoprene rubber ((C4H8)x(C5H8)y(Br2)z; x=7071, y=59,
z=50), also known as “BIIR,” submitted
a petition in accordance with Rev. Proc.
2022-26 requesting to add BIIR to the
List. According to the petition, the tax-

able chemicals isobutylene (an isomer of
butylene) and bromine constitute 99.01
percent by weight of the materials used to
produce BIIR, based on the predominant
method of production.
(a) Determination. Bromobutyl isobutylene isoprene rubber ((C4H8)x(C5H8)
(Br2)z; x=7071, y=59, z=50) is added to
y
the list of taxable substances under section
4672(a). Other pertinent information is as
follows:
(1) Predominant method of production: The predominant method of regular butyl rubber production is using a
carbocationic polymerization reaction
of isobutylene and a comonomer of isoprene. The catalyst system used is typically composed of aluminum chloride,
boron trifluoride or similar dissolved in
a methyl chloride solvent. Monomer feed
of isobutylene and isoprene dissolved
in a methyl chloride solvent are fed to a
reactor operated at approximately -100°C
to control the rapid exothermic polymerization reaction generating a high molecular weight butyl rubber polymer. To
obtain this high molecular weight polymer it is necessary for the feed monomers
to be as pure as possible ensuring that the
feed system stays as dry as possible. The
methyl chloride and unreacted monomers
are flashed overhead and recycled back to
the feed system while the polymer is precipitated out as a solid which is finished
and packaged.
The polymerization process for BIIR
starts with the exact same process for regular butyl rubber outlined above. A subsequent halogenation step is then carried out
in a well agitated vessel to ionically substitute a bromine molecule to the polymer
backbone while the polymer is dissolved
in an appropriate solvent. The solvent
is then flashed precipitating out a solid
which is then baled and packaged.
(2) Stoichiometric material consumption equation:
7071 C4H8 (isobutylene) + 59 C5H8
(isoprene) + 50 Br2 (bromine) →
[7071 C4H8 + 59 C5H8 + 50 Br2]
(BIIR)

The petition, and consequently the notice of filing, inadvertently omitted “x H2” from the products side of the stoichiometric material consumption equation. This omission has no impact on
the weight or value test. For clarity “x H2” has been included here.
2
The Notice of Filing erroneously stated that the HTSUS number as “4002.59.000” and the Schedule B number as “4002.59.000.” These errors are corrected here.
1

October 6, 2025

458

Bulletin No. 2025–41

(3) Reasons for the determination:
The BIIR petition was filed on April 8,
2025.3 The notice of filing summarizing
the petition and requesting comments was
published in the Federal Register (90 FR
20346) on May 13, 2025. The Treasury
Department and the IRS received no written comments in response to the notice
of filing. A public hearing was neither
requested nor held.
The Secretary followed the process
in section 4672(a)(2)(B) in making this
determination. A review of the stoichiometric material consumption equation and
other information in the petition shows
that the taxable chemicals isobutylene (an
isomer of butylene) and bromine constitute more than 20 percent by weight of the
materials used in the production of BIIR,
based on the predominant method of production. Therefore, the test in section
4672(a)(2)(B) is satisfied.
(4) Date of determination: September
15, 2025.
(5) Effective dates for addition of BIIR
to the List:
(i) Effective date for purposes of the
section 4671 tax (see section 11.01 of Rev.
Proc. 2022-26): January 1, 2026
(ii) Effective date for purposes of refund
claims under section 4662(e) (see sections
11.02 and 11.03 of Rev. Proc. 2022-26, as
modified by section 3 of Rev. Proc. 202320): July 1, 2022
(6) Tax rate prescribed by the Secretary: $9.63 per ton. The conversion factors for the taxable chemicals used in the
production of BIIR are 0.97 for butylene
and 0.02 for bromine. The tax rate is
calculated by adding the products of the
conversion factor for each taxable chemical and the tax rate for that taxable chemical: ((0.97 x $9.74) + (0.02 x $8.90) =
$9.63).
(b) Classification numbers.
(1) The Secretary has no basis to object
to the following proposed classification
numbers:
(i) HTSUS number: 4002.39.00
(ii) Schedule B number: 4002.39.00
(iii) CAS number: 68441-14-5
(2) The Secretary is unable to confirm the following proposed classification
numbers: Not applicable.

3

16. Determination to Add Chlorobutyl
Isobutylene Isoprene Rubber ((C4H8)
(C5H8)y(Cl2)z); x=7036, y=88, z=70) to
x
the List
Exxon Mobil Corporation, an exporter
of chlorobutyl isobutylene isoprene rubber ((C4H8)x(C5H8)y(Cl2)z); x=7036, y=88,
z=70), also known as “CIIR,” submitted
a petition in accordance with Rev. Proc.
2022-26 requesting to add CIIR to the
List. According to the petition, the taxable
chemicals isobutylene (an isomer of butylene) and chlorine constitute 98.50 percent
by weight of the materials used to produce
CIIR, based on the predominant method
of production.
(a) Determination. Chlorobutyl isobutylene isoprene rubber ((C4H8)x(C5H8)
(Cl2)z); x=7036, y=88, z=70) is added to
y
the list of taxable substances under section
4672(a). Other pertinent information is as
follows:
(1) Predominant method of production:
The predominant method of production
of regular butyl rubber is using a carbocationic polymerization reaction of isobutylene and a comonomer of isoprene. The
catalyst system used is typically composed
of aluminum chloride, boron trifluoride
or similar with an initiator dissolved in a
methyl chloride solvent. Monomer feed
of isobutylene and isoprene dissolved in a
methyl chloride solvent are fed to a reactor operated at approximately -100⁰C to
control the rapid exothermic polymerization reaction generating a high molecular
weight regular butyl rubber polymer. To
obtain this high molecular weight polymer
it is necessary for the feed monomers to be
as pure as possible as well as ensuring that
the feed system stays as dry as possible.
The methyl chloride and unreacted monomers are flashed overhead and recycled
back to the feed system while the polymer
is precipitated out as a solid which is then
baled and packaged.
The polymerization process for CIIR
starts with the exact same process for regular butyl rubber outlined above. A subsequent halogenation step is then carried out
in a well agitated vessel to ionically substitute a chlorine molecule to the polymer
backbone while the polymer is dissolved

in an appropriate solvent. The solvent
is then flashed, precipitating out a solid
which is then baled and packaged.
(2) Stoichiometric material consumption equation:
7036 C4H8 (isobutylene) + 88 C5H8
(isoprene) + 70 Cl2 (chlorine) → [7036
C4H8 + 88 C5H8 + 70 Cl2] (CIIR)
(3) Reasons for the determination:
The CIIR petition was filed on April 8,
2025. The notice of filing summarizing
the petition and requesting comments was
published in the Federal Register (90 FR
20350) on May 13, 2025. The Treasury
Department and the IRS received no written comments in response to the notice
of filing. A public hearing was neither
requested nor held.
The Secretary followed the process
in section 4672(a)(2)(B) in making this
determination. A review of the stoichiometric material consumption equation
and other information in the petition
shows that the taxable chemicals isobutylene (an isomer of butylene) and chlorine constitute more than 20 percent by
weight of the materials used in the production of CIIR, based on the predominant method of production. Therefore,
the test in section 4672(a)(2)(B) is satisfied.
(4) Date of determination: September
15, 2025.
(5) Effective dates for addition of CIIR
to the List:
(i) Effective date for purposes of the
section 4671 tax (see section 11.01 of Rev.
Proc. 2022-26): January 1, 2026
(ii) Effective date for purposes of refund
claims under section 4662(e) (see sections
11.02 and 11.03 of Rev. Proc. 2022-26, as
modified by section 3 of Rev. Proc. 202320): July 1, 2022
(6) Tax rate prescribed by the Secretary: $9.50 per ton. The conversion factors for the taxable chemicals used in the
production of CIIR are 0.97 for butylene
and 0.01 for chlorine. The tax rate is calculated by adding the products of the conversion factor for each taxable chemical
and the tax rate for that taxable chemical:
((0.97 x $9.74) + (0.01 x $5.40) = $9.50).

The Notice of Filing erroneously stated the year of filing as 2023. This error is corrected here.

Bulletin No. 2025–41

459

October 6, 2025

(b) Classification numbers.
(1) The Secretary has no basis to object
to the following proposed classification
numbers:
(i) HTSUS number: 4002.39.00
(ii) Schedule B number: 4002.39.00
(iii) CAS number: 68081-82-3
(2) The Secretary is unable to confirm the following proposed classification
numbers: Not applicable.
17. Determination to Add DIPE–Diisopropyl Ether to the List
Exxon Mobil Corporation, an exporter
of DIPE–di-isopropyl ether submitted
a petition in accordance with Rev. Proc.
2022-26 requesting to add DIPE–di-isopropyl ether to the List. According to the
petition, the taxable chemical propylene
constitutes 82.40 percent by weight of the
materials used to produce DIPE–di-isopropyl ether, based on the predominant
method of production.
(a) Determination. DIPE–di-isopropyl
ether is added to the list of taxable substances under section 4672(a). Other pertinent information is as follows:
(1) Predominant method of production:
DIPE–di-isopropyl ether is produced via
isopropyl alcohol (IPA) production using
a two-step indirect hydration process.
A mixed propane/propylene stream is
reacted with aqueous sulfuric acid to form
a H2SO4/propylene extract. The formed
isopropyl hydrogen sulfate is further
reacted with additional IPA under acidic
conditions to form DIPE–di-isopropyl
ether such that two moles of isopropanol
are converted to one mole of DIPE–di-isopropyl ether and one mole of water.
(2) Stoichiometric material consumption equation:
2 C3H6 [propylene] + H2O [water] →
C6H14O [DIPE–di-isopropyl ether]
(3) Reasons for the determination:
The DIPE–di-isopropyl ether petition was
filed on May 1, 2025. The notice of filing
summarizing the petition and requesting
comments was published in the Federal
Register (90 FR 21126) on May 16, 2025.
The Treasury Department and the IRS
received no written comments in response
to the notice of filing. A public hearing
was neither requested nor held.

October 6, 2025

The Secretary followed the process
in section 4672(a)(2)(B) in making this
determination. A review of the stoichiometric material consumption equation and
other information in the petition shows
that the taxable chemical propylene constitutes more than 20 percent by weight
of the materials used in the production
of DIPE–di-isopropyl ether, based on
the predominant method of production.
Therefore, the test in section 4672(a)(2)
(B) is satisfied.
(4) Date of determination: September
15, 2025.
(5) Effective dates for addition of
DIPE–di-isopropyl ether to the List:
(i) Effective date for purposes of the
section 4671 tax (see section 11.01 of Rev.
Proc. 2022-26): January 1, 2026
(ii) Effective date for purposes of refund
claims under section 4662(e) (see sections
11.02 and 11.03 of Rev. Proc. 2022-26, as
modified by section 3 of Rev. Proc. 202320): July 1, 2022
(6) Tax rate prescribed by the Secretary: $7.99 per ton. The conversion
factor for the propylene used in the production of DIPE–di-isopropyl ether is
0.82. The tax rate is calculated by multiplying the conversion factor by the
tax rate for propylene: (0.82 x $9.74 =
$7.99).
(b) Classification numbers.
(1) The Secretary has no basis to object
to the following proposed classification
numbers:
(i) HTSUS number: 2909.19.18.00
(ii) Schedule B number: 2909.19.18.00
(iii) CAS number: 108-20-3
(2) The Secretary is unable to confirm the following proposed classification
numbers: Not applicable.
18. Determination to Add Di-isodecyl
Phthalate to the List
Exxon Mobil Corporation, an exporter
of di-isodecyl phthalate, submitted a petition in accordance with Rev. Proc. 202226 requesting to add di-isodecyl phthalate
to the List. According to the petition, the
taxable chemicals propylene and orthoxylene (an isomer of xylene) constitute
64.50 percent by weight of the materials
used to produce di-isodecyl phthalate,
based on the predominant method of production.

460

(a) Determination. Di-isodecyl phthalate is added to the list of taxable substances under section 4672(a). Other pertinent information is as follows:
(1) Predominant method of production:
The predominant method of producing
di-isodecyl phthalate is via esterification.
This process can be readily carried
out in heated kettles with agitation and
provision for water takeoff. Esterification
catalysts (e.g., sulfuric acid or p-toluenesulfonic acid) speed the reaction and are
neutralized, washed, and then removed.
The purity requirements for commercial
plasticizers are very high; phthalate esters
are usually colorless and are mostly odorless. In the case of phthalates, the esterification is carried out through the reaction
of phthalic anhydride and 2-ethylhexanol
to produce dioctyl phthalate (DOP).
This reaction usually requires an
excess of alcohol, which is readily recycled. Analogous syntheses yield aliphatic
dicarboxylic acid esters, benzoates, and
trimellitates.
(2) Stoichiometric material consumption equation:
5.45 C3H6 [propylene] + 0.35 C5H10
[amylene] + 2 CO [carbon monoxide]
+ 4 H2 [hydrogen] + C8H10 [orthoxylene] + 3 O2 [oxygen] → C28H46O4
[di-isodecyl phthalate] + 4 H2O
[water]
(3) Reasons for the determination:
The di-isodecyl phthalate petition was
filed on April 8, 2025. The notice of filing
summarizing the petition and requesting
comments was published in the Federal
Register (90 FR 20354) on May 13, 2025.
The Treasury Department and the IRS
received no written comments in response
to the notice of filing. A public hearing
was neither requested nor held.
The Secretary followed the process
in section 4672(a)(2)(B) in making this
determination. A review of the stoichiometric material consumption equation and
other information in the petition shows
that the taxable chemicals propylene and
orthoxylene (an isomer of xylene) constitute more than 20 percent by weight of the
materials used in the production of di-isodecyl phthalate, based on the predominant
method of production. Therefore, the test
in section 4672(a)(2)(B) is satisfied.

Bulletin No. 2025–41

(4) Date of determination: September
15, 2025.
(5) Effective dates for addition of
di-isodecyl phthalate to the List:
(i) Effective date for purposes of the
section 4671 tax (see section 11.01 of Rev.
Proc. 2022-26): January 1, 2026
(ii) Effective date for purposes of refund
claims under section 4662(e) (see sections
11.02 and 11.03 of Rev. Proc. 2022-26, as
modified by section 3 of Rev. Proc. 202320): July 1, 2022
(6) Tax rate prescribed by the Secretary: $7.31 per ton. The conversion factors
for the taxable chemicals used in the production of di-isodecyl phthalate are 0.51
for propylene and 0.24 for xylene. The tax
rate is calculated by adding the products
of the conversion factor for each taxable
chemical and the tax rate for that taxable
chemical: ((0.51 x $9.74) + (0.24 x $9.74)
= $7.31).
(b) Classification numbers.
(1) The Secretary has no basis to object
to the following proposed classification
numbers: Not applicable.
(2) The Secretary is unable to confirm the following proposed classification
numbers:
(i) HTSUS number: 2917.33.00.10
(ii) Schedule B number: 2917.33.00.10
(iii) CAS number: 68515-49-1
19. Determination to Add Di-isononyl
Adipate to the List
Exxon Mobil Corporation, an exporter
of di-isononyl adipate, also known as
“DINA,” submitted a petition in accordance with Rev. Proc. 2022-26 requesting
to add DINA to the List. According to the
petition, the taxable chemicals propylene,
benzene, and nitric acid constitute 79.20
percent by weight of the materials used to
produce DINA, based on the predominant
method of production.
(a) Determination. Di-isononyl adipate
is added to the list of taxable substances
under section 4672(a). Other pertinent
information is as follows:
(1) Predominant method of production:
DINA is produced via esterification. The
di-isononyl adipate di-ester is made by
reacting primary isononyl (C9) alcohol
with adipic acid. The ester is produced by
esterification of two moles of isononyl C9

Bulletin No. 2025–41

alcohol and one mole of adipic acid in the
presence of a catalyst.
By using excess alcohol (up to 30%
molar excess of C9 alcohol) and removing the water, the equilibrium is shifted
towards the formation of the di-ester. The
reactants are charged into a reactor and
heated up. The reaction rate is accelerated by using, for example, tetra-n-butyl
titanate introduced at high temperature
(140°C – 250°C), while removing the
water formed.
Excess alcohol is distilled from the
ester by vacuum prior to neutralization and
recycled into subsequent batches. The final
ester is purified by neutralizing with a base
such as an aqueous solution of sodium carbonate. The remaining excess water is distilled off and the ester is then filtered using
filter agents. The degree of purity of the
ester has a minimum 99.0 wt%.
(2) Stoichiometric material consumption equation:
4.82 C3H6 [propylene] + 0.30 C5H10
[amylene] + 2 CO [carbon monoxide]
+ 7 H2 [hydrogen] + C6H6 [benzene]
+ 0.50 O2 [oxygen] + 2 HNO3 [nitric
acid] → C24H46O4 [di-isononyl adipate] + 4 H2O [water] + N2O [nitrous
oxide]
(3) Reasons for the determination:
The DINA petition was filed on May 1,
2025. The notice of filing summarizing
the petition and requesting comments was
published in the Federal Register (90 FR
21131) on May 16, 2025. The Treasury
Department and the IRS received no written comments in response to the notice
of filing. A public hearing was neither
requested nor held.
The Secretary followed the process
in section 4672(a)(2)(B) in making this
determination. A review of the stoichiometric material consumption equation and
other information in the petition shows
that the taxable chemicals propylene,
benzene, and nitric acid constitute more
than 20 percent by weight of the materials used in the production of DINA, based
on the predominant method of production.
Therefore, the test in section 4672(a)(2)
(B) is satisfied.
(4) Date of determination: September
15, 2025.

461

(5) Effective dates for addition of DINA
to the List:
(i) Effective date for purposes of the
section 4671 tax (see section 11.01 of Rev.
Proc. 2022-26): January 1, 2026
(ii) Effective date for purposes of refund
claims under section 4662(e) (see sections
11.02 and 11.03 of Rev. Proc. 2022-26, as
modified by section 3 of Rev. Proc. 202320): July 1, 2022
(6) Tax rate prescribed by the Secretary: $7.07 per ton. The conversion factors
for the taxable chemicals used in the production of DINA are 0.51 for propylene,
0.20 for benzene, and 0.32 for nitric acid.
The tax rate is calculated by adding the
products of the conversion factor for each
taxable chemical and the tax rate for that
taxable chemical: ((0.51 x $9.74) + (0.20
x $9.74) + (0.32 x $0.48) = $7.07).
(b) Classification numbers.
(1) The Secretary has no basis to object
to the following proposed classification
numbers:
(i) HTSUS number: 2917.12.20.00
(ii) Schedule B number: 2917.12.2000
(iii) CAS number: 33703–08–1
(2) The Secretary is unable to confirm the following proposed classification
numbers: Not applicable.
20. Determination to Add Di-isononyl
Phthalate to the List
Exxon Mobil Corporation, an exporter
of di-isononyl phthalate, submitted a petition in accordance with Rev. Proc. 2022-26
requesting to add di-isononyl phthalate to
the List. According to the petition, the taxable chemicals propylene and orthoxylene
(an isomer of xylene) constitute 62.90
percent by weight of the materials used to
produce di-isononyl phthalate, based on the
predominant method of production.
(a) Determination. Di-isononyl phthalate is added to the list of taxable substances under section 4672(a). Other pertinent information is as follows:
(1) Predominant method of production:
The predominant method of producing
di-isononyl phthalate is via esterification.
Most plasticizers are products of simple esterification reactions, which can be
readily carried out in heated kettles with
agitation and provision for water takeoff.
While some plants produce plasticizers

October 6, 2025

by such batch methods, newer, highly
automated plants operate continuously,
particularly if they emphasize a single
product. Esterification catalysts (e.g.
sulfuric acid or p-toluenesulfonic acid)
speed the reaction and are neutralized,
washed, and then removed. The purity
requirements for commercial plasticizers
are very high; phthalate esters are usually
colorless and are mostly odorless. The
reaction usually requires an excess of
alcohol, which is readily recycled. Analogous syntheses yield aliphatic dicarboxylic acid esters, benzoates, and trimellitates.
The hydrogen used for these reactions
is not produced from steam-methane
reforming; the source is from a POx reactor, which feeds liquids, not methane. The
POx process is an industrial process that
converts hydrocarbons feeds into syngas
(a combination of H2 and CO gas). The
hydrocarbon feed is in the liquid state;
it does not feed gas (such as methane)
or solids. The unit feeds a variety of liquid hydrocarbons such as paraffins, olefins, and aromatics in the C9-C20 range,
obtained from the refinery pipestills and
other chemicals units.
(2) Stoichiometric material consumption equation:
5.12 x 0.94 C3H6 [propylene] + 5.12 x
0.06 C5H10 [amylene] + 2 CO [carbon
monoxide] + 4 H2 [hydrogen] + C8H10
[orthoxylene] + 3 O2 [oxygen] →
C26H42O4 [di-isononyl phthalate] + 4
H2O [water]
(3) Reasons for the determination:
The di-isononyl phthalate petition
was filed on May 1, 2025. The notice
of filing summarizing the petition and
requesting comments was published in
the Federal Register (90 FR 20551) on
May 14, 2025. The Treasury Department and the IRS received no written
comments in response to the notice of
filing. A public hearing was neither
requested nor held.
The Secretary followed the process
in section 4672(a)(2)(B) in making this
determination. A review of the stoichiometric material consumption equation and

other information in the petition shows
that the taxable chemicals propylene and
orthoxylene (an isomer of xylene) constitute more than 20 percent by weight
of the materials used in the production of
di-isononyl phthalate, based on the predominant method of production. Therefore, the test in section 4672(a)(2)(B) is
satisfied.
(4) Date of determination: September
15, 2025.
(5) Effective dates for addition of
di-isononyl phthalate to the List:
(i) Effective date for purposes of the
section 4671 tax (see section 11.01 of Rev.
Proc. 2022-26): January 1, 2026
(ii) Effective date for purposes of refund
claims under section 4662(e) (see sections
11.02 and 11.03 of Rev. Proc. 2022-26, as
modified by section 3 of Rev. Proc. 202320): July 1, 2022
(6) Tax rate prescribed by the Secretary: $7.11 per ton. The conversion factors
for the taxable chemicals used in the production of di-isononyl phthalate are 0.48
for propylene and 0.25 for xylene. The tax
rate is calculated by adding the products
of the conversion factor for each taxable
chemical and the tax rate for that taxable
chemical: ((0.48 x $9.74) + (0.25 x $9.74)
= $7.11).
(b) Classification numbers.
(1) The Secretary has no basis to object
to the following proposed classification
numbers: Not applicable.
(2) The Secretary is unable to confirm the following proposed classification
numbers:
(i) HTSUS number: 2917.33.00.50
(ii) Schedule B number: 2917.33.00.50
(iii) CAS number: 68515-48-0
21. Determination to Add Di-tridecyl
Phthalate to the List
Exxon Mobil Corporation, an exporter
of di-tridecyl phthalate, submitted a petition in accordance with Rev. Proc. 202226 requesting to add di-tridecyl phthalate
to the List. According to the petition, the
taxable chemicals propylene and orthoxylene (an isomer of xylene) constitute
68.10 percent by weight of the materials used to produce di-tridecyl phthalate,

based on the predominant method of production.
(a) Determination. Di-tridecyl phthalate is added to the list of taxable substances under section 4672(a). Other pertinent information is as follows:
(1) Predominant method of production:
The predominant method of producing
di-tridecyl phthalate4 is via esterification.
This process can be readily carried
out in heated kettles with agitation and
provision for water takeoff. Esterification catalysts (e.g., sulfuric acid or p-toluenesulfonic acid) speed the reaction
and are neutralized, washed, and then
removed. The purity requirements for
commercial plasticizers are very high;
phthalate esters are usually colorless
and are mostly odorless. In the case of
phthalates, the esterification is carried
out through the reaction of phthalic
anhydride and 2-ethylhexanol to produce
dioctyl phthalate (DOP).
This reaction usually requires an
excess of alcohol, which is readily recycled. Analogous syntheses yield aliphatic
dicarboxylic acid esters, benzoates, and
trimellitates.
(2) Stoichiometric material consumption equation:
7.70 x 0.94 C3H6 [propylene] + 7.70 x
0.06 C5H10 [amylene] + 2 CO [carbon
monoxide] + 4 H2 [hydrogen] + C8H10
[orthoxylene] + 3 O2 [oxygen] →
C34H58O4 [di-tridecyl phthalate] + 4
H2O [water]
(3) Reasons for the determination: The
di-tridecyl phthalate petition was filed on
April 8, 2025. The notice of filing summarizing the petition and requesting
comments was published in the Federal
Register (90 FR 20352) on May 13, 2025.
The Treasury Department and the IRS
received no written comments in response
to the notice of filing. A public hearing
was neither requested nor held.
The Secretary followed the process
in section 4672(a)(2)(B) in making this
determination. A review of the stoichiometric material consumption equation
and other information in the petition
shows that the taxable chemicals pro-

The Notice of Filing for di-tridecyl phthalate had a typographical error misstating the name of the taxable substance in the predominant method of production section. This error is corrected
here.
4

October 6, 2025

462

Bulletin No. 2025–41

pylene and orthoxylene (an isomer of
xylene) constitute more than 20 percent
by weight of the materials used in the production of di-tridecyl phthalate, based on
the predominant method of production.
Therefore, the test in section 4672(a)(2)
(B) is satisfied.
(4) Date of determination: September
15, 2025.
(5) Effective dates for addition of di-tridecyl phthalate to the List:
(i) Effective date for purposes of the
section 4671 tax (see section 11.01 of Rev.
Proc. 2022-26): January 1, 2026
(ii) Effective date for purposes of refund
claims under section 4662(e) (see sections
11.02 and 11.03 of Rev. Proc. 2022-26, as
modified by section 3 of Rev. Proc. 202320): July 1, 2022
(6) Tax rate prescribed by the Secretary: $7.50 per ton. The conversion factors
for the taxable chemicals used in the production of di-tridecyl phthalate are 0.57
for propylene and 0.20 for xylene. The tax
rate is calculated by adding the products
of the conversion factor for each taxable
chemical and the tax rate for that taxable
chemical: ((0.57 x $9.74) + (0.20 x $9.74)
= $7.50).
(b) Classification numbers.
(1) The Secretary has no basis to object
to the following proposed classification
numbers: Not applicable.
(2) The Secretary is unable to confirm the following proposed classification
numbers:
(i) HTSUS number: 2917.34.01.50
(ii) Schedule B number: 2917.34.0150
(iii) CAS number: 68515-47-9
22. Determination to Add Ethylene
Propylene Diene (EPDM) Rubber
((C2H4)x(C3H6)y(C9H12)z; x=5134,
y=2250, z=98) to the List
Exxon Mobil Corporation, an exporter
of ethylene propylene diene (EPDM)
rubber ((C2H4)x(C3H6)y(C9H12)z; x=5134,
y=2250, z=98), submitted a petition in
accordance with Rev. Proc. 2022-26
requesting to add EPDM rubber ((C2H4)
(C3H6)y(C9H12)z; x=5134, y=2250, z=98)
x
to the List. According to the petition, the
taxable chemicals ethylene, propylene,
and butadiene constitute 97.41 percent by
weight of the materials used to produce
EPDM rubber ((C2H4)x(C3H6)y(C9H12)z;

Bulletin No. 2025–41

x=5134, y=2250, z=98), based on the predominant method of production.
(a) Determination. Ethylene propylene diene (EPDM) rubber ((C2H4)x(C3H6)
(C9H12)z; x=5134, y=2250, z=98) is added
y
to the list of taxable substances under section 4672(a). Other pertinent information
is as follows:
(1) Predominant method of production:
The predominant method of producing
EPDM rubber ((C2H4)x(C3H6)y(C9H12)z;
x=5134, y=2250, z=98) is copolymerization of ethylene and propylene with or
without a small amount of a non-conjugated diene.
(2) Stoichiometric material consumption equation:
5,134 C2H4 [ethylene] + 2,250 C3H6
[propylene] + 98 C4H6 [butadiene] +
98 C5H6 [cyclopentadiene] → (5,134
C2H4 + 2,250 C3H6 + 98 C9H12)
[EPDM]
(3) Reasons for the determination:
The EPDM rubber ((C2H4)x(C3H6)
(C9H12)z; x=5134, y=2250, z=98) petiy
tion was filed on May 1, 2025. The
notice of filing summarizing the petition
and requesting comments was published
in the Federal Register (90 FR 21825)
on May 21, 2025. The Treasury Department and the IRS received one non-substantive written comment regarding the
effect of EPDM on the environment
and wildlife in response to the notice
of filing. The comment did not address
whether EPDM rubber ((C2H4)x(C3H6)
(C9H12)z; x=5134, y=2250, z=98) meets
y
the weight or value test under section
4672(a)(2)(B). A public hearing was neither requested nor held.
The Secretary followed the process
in section 4672(a)(2)(B) in making this
determination. A review of the stoichiometric material consumption equation and
other information in the petition shows
that the taxable chemicals ethylene, propylene, and butadiene constitute more
than 20 percent by weight of the materials
used in the production of EPDM rubber
((C2H4)x(C3H6)y(C9H12)z; x=5134, y=2250,
z=98), based on the predominant method
of production. Therefore, the test in section 4672(a)(2)(B) is satisfied.
(4) Date of determination: September
15, 2025.

463

(5) Effective dates for addition of
EPDM rubber ((C2H4)x(C3H6)y(C9H12)z;
x=5134, y=2250, z=98) to the List:
(i) Effective date for purposes of the
section 4671 tax (see section 11.01 of Rev.
Proc. 2022-26): January 1, 2026
(ii) Effective date for purposes of refund
claims under section 4662(e) (see sections
11.02 and 11.03 of Rev. Proc. 2022-26, as
modified by section 3 of Rev. Proc. 202320): July 1, 2022
(6) Tax rate prescribed by the Secretary: $9.45 per ton. The conversion factors
for the taxable chemicals used in the production of EPDM rubber ((C2H4)x(C3H6)
(C9H12)z; x=5134, y=2250, z=98) are 0.57
y
for ethylene, 0.38 for propylene, and 0.02
for butadiene. The tax rate is calculated
by adding the products of the conversion
factor for each taxable chemical and the
tax rate for that taxable chemical: ((0.57
x $9.74) + (0.38 x $9.74) + (0.02 x $9.74)
= $9.45).
(b) Classification numbers.
(1) The Secretary has no basis to object
to the following proposed classification
numbers:
(i) HTSUS number: 4002.70.00
(ii) Schedule B number: 4002.70.0000
(iii) CAS number: 25034-71-3
(2) The Secretary is unable to confirm the following proposed classification
numbers: Not applicable.
23. Determination to Add Isodecyl
Alcohol to the List
Exxon Mobil Corporation, an exporter
of isodecyl alcohol, submitted a petition
in accordance with Rev. Proc. 2022-26
requesting to add isodecyl alcohol to
the List. According to the petition, the
taxable chemical propylene constitutes
72.00 percent by weight of the materials
used to produce isodecyl alcohol, based
on the predominant method of production.
(a) Determination. Isodecyl alcohol
is added to the list of taxable substances
under section 4672(a). Other pertinent
information is as follows:
(1) Predominant method of production:
The predominant method of producing isodecyl alcohol is in an oxonation reaction.
Plasticizer alcohols, including isodecyl
alcohol, are derived from the oxo reaction
with branched olefins. Refinery-connected

October 6, 2025

polygas units generate many of these olefins as purified cuts or fractions.
The hydrogen used for these reactions are not produced from steam-methane reforming. The source of hydrogen
is from a Pox reactor, which feeds liquids, not methane. The Pox process is an
industrial process that converts hydrocarbons feeds into syngas (a combination of
hydrogen and carbon monoxide gas). The
hydrocarbon feed is in the liquid state. The
unit feeds a variety of liquid hydrocarbons
such as paraffins, olefins, and aromatics in
the C5-C20 range, obtained from the refinery pipestills and other chemicals units.
(2) Stoichiometric material consumption equation:
2.88 x 0.94 C3H6 [propylene] + 2.88
x 0.06 C5H10 [amylene] + CO [carbon monoxide] + 2 H2 [hydrogen] →
C10H22O [isodecyl alcohol]
(3) Reasons for the determination: The
isodecyl alcohol petition was filed on May
1, 2025. The notice of filing summarizing
the petition and requesting comments was
published in the Federal Register (90 FR
21129) on May 16, 2025. The Treasury
Department and the IRS received no written comments in response to the notice
of filing. A public hearing was neither
requested nor held.
The Secretary followed the process
in section 4672(a)(2)(B) in making this
determination. A review of the stoichiometric material consumption equation
and other information in the petition
shows that the taxable chemical propylene constitutes more than 20 percent by
weight of the materials used in the production of isodecyl alcohol, based on
the predominant method of production.
Therefore, the test in section 4672(a)(2)
(B) is satisfied.
(4) Date of determination: September
15, 2025.
(5) Effective dates for addition of isodecyl alcohol to the List:
(i) Effective date for purposes of the
section 4671 tax (see section 11.01 of Rev.
Proc. 2022-26): January 1, 2026
(ii) Effective date for purposes of refund
claims under section 4662(e) (see sections
11.02 and 11.03 of Rev. Proc. 2022-26, as
modified by section 3 of Rev. Proc. 202320): July 1, 2022

October 6, 2025

(6) Tax rate prescribed by the Secretary: $7.01 per ton. The conversion factor
for the propylene used in the production
of isodecyl alcohol is 0.72. The tax rate is
calculated by multiplying the conversion
factor by the tax rate for propylene: (0.72
x $9.74 = $7.01).
(b) Classification numbers.
(1) The Secretary has no basis to object
to the following proposed classification
number: CAS number: 68526-85-2
(2) The Secretary is unable to confirm the following proposed classification
numbers:
(i) HTSUS number: 3823.70.60.00
(ii) Schedule B number: 3823.70.6000
24. Determination to Add Isodecyl
Benzoate to the List
Exxon Mobil Corporation, an exporter
of isodecyl benzoate, submitted a petition
in accordance with Rev. Proc. 2022-26
requesting to add isodecyl benzoate to
the List. According to the petition, the
taxable chemicals propylene and toluene
constitute 69.10 percent by weight of the
materials used to produce isodecyl benzoate, based on the predominant method of
production.
(a) Determination. Isodecyl benzoate
is added to the list of taxable substances
under section 4672(a). Other pertinent
information is as follows:
(1) Predominant method of production:
The predominant method of producing
isodecyl benzoate is via esterification. The
isodecyl benzoate ester is made by reacting primary isodecyl (C10) alcohol with
benzoic acid. The ester is produced by
esterification of one mole of isodecyl C10
alcohol and one mole of benzoic acid in
the presence of a catalyst.
By using excess alcohol (up to 30%
molar excess of C10 alcohol) and removing the water, the equilibrium is shifted
towards the formation of the ester. The
reactants are charged into a reactor and
heated up. The reaction rate is accelerated by using, for example, tetra-n-butyl
titanate introduced at high temperature
(140°C – 250°C), while removing the
water formed.
Excess alcohol is distilled from the
ester by vacuum prior to neutralization
and recycled into subsequent batches.
The final ester is purified by neutralizing

464

with a base such as an aqueous solution of
sodium carbonate. The remaining excess
water is distilled off and the ester is then
filtered using filter agents. The degree of
purity of the ester has a minimum 99.0
wt%.
(2) Stoichiometric material consumption equation:
2.71 C3H6 [propylene] + 0.17 C5H10
[amylene] + CO [carbon monoxide] +
2 H2 [hydrogen] + C6H5CH3 [toluene]
+ 1.5 O2 [oxygen] → C17H26O2 [isodecyl benzoate] + 2 H2O [water]
(3) Reasons for the determination:
The isodecyl benzoate petition was
filed on May 1, 2025. The notice of
filing summarizing the petition and
requesting comments was published in
the Federal Register (90 FR 21130) on
May 16, 2025. The Treasury Department and the IRS received no written
comments in response to the notice of
filing. A public hearing was neither
requested nor held.
The Secretary followed the process
in section 4672(a)(2)(B) in making this
determination. A review of the stoichiometric material consumption equation and
other information in the petition shows
that the taxable chemicals propylene and
toluene constitute more than 20 percent
by weight of the materials used in the production of isodecyl benzoate, based on
the predominant method of production.
Therefore, the test in section 4672(a)(2)
(B) is satisfied.
(4) Date of determination: September
15, 2025.
(5) Effective dates for addition of isodecyl benzoate to the List:
(i) Effective date for purposes of the
section 4671 tax (see section 11.01 of Rev.
Proc. 2022-26): January 1, 2026
(ii) Effective date for purposes of refund
claims under section 4662(e) (see sections
11.02 and 11.03 of Rev. Proc. 2022-26, as
modified by section 3 of Rev. Proc. 202320): July 1, 2022
(6) Tax rate prescribed by the Secretary: $7.60 per ton. The conversion factors
for the taxable chemicals used in the production of isodecyl benzoate are 0.43 for
propylene and 0.35 for toluene. The tax
rate is calculated by adding the products
of the conversion factor for each taxable

Bulletin No. 2025–41

chemical and the tax rate for that taxable
chemical: ((0.43 x $9.74) + (0.35 x $9.74)
= $7.60).
(b) Classification numbers.
(1) The Secretary has no basis to object
to the following proposed classification
numbers: Not applicable.
(2) The Secretary is unable to confirm the following proposed classification
numbers:
(i) HTSUS number: 2916.31.50.00
(ii) Schedule B number: 2916.31.0002
(iii) CAS number: 131298-44-7
25. Determination to Add Isooctyl
Alcohol to the List
Exxon Mobil Corporation, an exporter
of isooctyl alcohol, submitted a petition
in accordance with Rev. Proc. 2022-26
requesting to add isooctyl alcohol to the
List. According to the petition, the taxable chemical propylene constitutes 68.10
percent by weight of the materials used
to produce isooctyl alcohol, based on the
predominant method of production.
(a) Determination. Isooctyl alcohol
is added to the list of taxable substances
under section 4672(a). Other pertinent
information is as follows:
(1) Predominant method of production: The predominant method of producing isooctyl alcohol is in an oxonation
reaction. Plasticizer alcohols, including
isooctyl alcohol, are derived from the oxo
reaction with branched olefins. Refinery-connected polygas units generate
many of these olefins as purified cuts or
fractions. For example, isooctyl alcohol
is produced from heptene, which is an
isomeric mixture of C7 olefins that are
derived from the reaction of propylene
and butylenes. The extent of branching
in heptane depends on the reaction conditions and feedstock ratio at the polygas
units. Since these conditions are variable,
the specifications of the alcohol product
may vary among producers.
The hydrogen used for these reactions
are not produced from steam-methane
reforming. The source of hydrogen is
from POx reactor, which feeds liquids, not
methane. The POx process is an industrial
process that converts hydrocarbons feeds
into syngas (a combination of hydrogen
and carbon monoxide gas). The hydrocarbon feed is in the liquid state. The unit

Bulletin No. 2025–41

feeds a variety of liquid hydrocarbons
such as paraffins, olefins, and aromatics
in the C5-C20 range, obtained from the
refinery pipestills and other chemicals
units.
(2) Stoichiometric material consumption equation:
2.24 x 0.94 C3H6 [propylene] + 2.24 x
0.06 C5H10 [amylene] + CO [carbon
monoxide] + 2 H2 [hydrogen] →
C8H18O [isooctyl alcohol]
(3) Reasons for the determination:
The isooctyl alcohol petition was filed
on May 1, 2025. The notice of filing
summarizing the petition and requesting comments was published in the Federal Register (90 FR 21126) on May 16,
2025. The Treasury Department and the
IRS received one non-substantive written comment regarding the importance
of evaluating the data in response to the
notice of filing. The comment did not
address whether isooctyl alcohol meets
the weight or value test under section
4672(a)(2)(B). A public hearing was neither requested nor held.
The Secretary followed the process
in section 4672(a)(2)(B) in making this
determination. A review of the stoichiometric material consumption equation
and other information in the petition
shows that the taxable chemical propylene constitutes more than 20 percent by
weight of the materials used in the production of isooctyl alcohol, based on
the predominant method of production.
Therefore, the test in section 4672(a)(2)
(B) is satisfied.
(4) Date of determination: September
15, 2025.
(5) Effective dates for addition of
isooctyl alcohol to the List:
(i) Effective date for purposes of the
section 4671 tax (see section 11.01 of Rev.
Proc. 2022-26): January 1, 2026
(ii) Effective date for purposes of refund
claims under section 4662(e) (see sections
11.02 and 11.03 of Rev. Proc. 2022-26, as
modified by section 3 of Rev. Proc. 202320): July 1, 2022
(6) Tax rate prescribed by the Secretary: $6.62 per ton. The conversion factor
for the propylene used in the production
of isooctyl alcohol is 0.68. The tax rate is
calculated by multiplying the conversion

465

factor by the tax rate for propylene: (0.68
x $9.74 = $6.62).
(b) Classification numbers.
(1) The Secretary has no basis to object
to the following proposed classification
numbers:
(i) HTSUS number: 2905.16.00.50
(ii) Schedule B number: 2905.16.0050
(iii) CAS number: 68526-83-0
(2) The Secretary is unable to confirm the following proposed classification
numbers: Not applicable.
26. Determination to Add Linear Nonyl
Phthalate to the List
Exxon Mobil Corporation, an exporter
of linear nonyl phthalate, submitted a petition in accordance with Rev. Proc. 2022-26
requesting to add linear nonyl phthalate to
the List. According to the petition, the taxable chemicals ethylene and orthoxylene
(an isomer of xylene) constitute 67.40 percent by weight of the materials used to produce linear nonyl phthalate, based on the
predominant method of production.
(a) Determination. Linear nonyl
phthalate is added to the list of taxable
substances under section 4672(a). Other
pertinent information is as follows:
(1) Predominant method of production:
The predominant method of producing
linear nonyl phthalate is via esterification.
The linear nonyl phthalate di-ester is
made by reacting a mix of primary C9
alcohol with phthalic anhydride. The ester
is produced by esterification of two moles
of a linear C9 alcohol with one mole of
phthalic anhydride in the presence of an
acidic catalyst.
By using excess alcohol (up to 25%
molar excess of C9 alcohol) and removing the water, the equilibrium is shifted
towards the formation of the di-ester. The
reactants are charged into a reactor and
heated up. The reaction rate is accelerated by using, for example, tetra-n-butyl
titanate introduced at high temperature
(140°C – 250°C), while removing the
water fo

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Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/agency%3Airs%3A3644f32beb69239d. Public record. Not legal advice.