(Rev. December 2025)

Instructions for

Form 1120-X

(Rev. December 2025)

Amended U.S. Corporation Income Tax Return

Section references are to the Internal Revenue Code

unless otherwise noted.

Future Developments

For the latest information about developments affecting

Form 1120-X and its instructions, such as legislation

enacted after they were published, go to IRS.gov/

Form1120X.

General Instructions

Section references are to the Internal Revenue Code

unless otherwise noted.

Purpose of Form

Use Form 1120-X to:

• Correct a Form 1120 (or Form 1120-A, if applicable) as

originally filed, or as later adjusted by an amended return,

a claim for refund, or an examination; or

• Make certain elections after the prescribed deadline

(see Regulations sections 301.9100-1 through 3) or any

other published guidance or administrative relief.

Do not use Form 1120-X to...

Instead, use...

Apply for a quick refund of

estimated tax

Form 4466, Corporation

Application for Quick Refund of

Overpayment of Estimated Tax.

Obtain a tentative refund of taxes

due to:

• A net operating loss (NOL)

carryback,

• A net capital loss carryback,

• An unused general business

credit carryback, or

• A claim of right adjustment

under section 1341(b)(1).

Form 1139, Corporation

Application for Tentative Refund.

Note: Use Form 1139 only if 1

year or less has passed since the

tax year in which the carryback or

adjustment occurred. Otherwise,

use Form 1120-X.

Request IRS approval for a

change in accounting method.

Form 3115, Application for

Change in Accounting Method.

When To File

File Form 1120-X only after the corporation has filed its

original return. Generally, Form 1120-X must be filed

within 3 years after the date the corporation filed its

original return or within 2 years after the date the

corporation paid the tax (if filing a claim for a refund),

whichever is later. A return filed before the due date is

considered filed on the due date. A Form 1120-X based

on an NOL carryback, a capital loss carryback, or general

business credit carryback generally must be filed within 3

years after the due date (including extensions) of the

return for the tax year of the NOL, capital loss, or unused

Dec 9, 2025

credit. A Form 1120-X based on a bad debt or worthless

security must be filed within 7 years after the due date of

the return for the tax year in which the debt or security

became worthless. See section 6511 for more details and

other special rules.

Note: It often takes 3 to 4 months to process Form

1120-X.

Private delivery services (PDSs). Corporations can

use certain PDSs designated by the IRS to meet the

“timely mailing as timely filing” rule for tax returns. See the

Instructions for Form 1120 for more information.

What To Attach

If the corrected amount involves an item of income,

deduction, or credit that must be supported with a

schedule, statement, or form, attach the appropriate

schedule, statement, or form to Form 1120-X. Include the

corporation’s name and employer identification number on

any attachments. See the instructions for the applicable

Form 1120 for the tax year of the claim for a list of forms

that may be required.

Tax Shelters

If the corporation’s return is being amended for a tax year

in which the corporation participated in a “reportable

transaction,” attach Form 8886, Reportable Transaction

Disclosure Statement. If a reportable transaction results in

a loss or credit carried back to a prior tax year, attach

Form 8886 for the carryback years.

Carryback Claims

If Form 1120-X is used as a carryback claim, attach

copies of Form 1120, page 1, and the tax computation

page, for both the year the loss or credit originated and for

the carryback year. Also attach any other forms,

schedules, or statements that are necessary to support

the claim, including a statement that shows all

adjustments required to figure any NOL that was carried

back. At the top of the forms or schedules attached, write

“Copy Only—Do Not Process.”

Carryback of an eligible small business credit

(ESBC). If the corporation is an eligible small business

(as defined in section 38(c)(5)(B)) and is using Form

1120-X to claim a carryback of an unused ESBC, enter

“SBJA 2012” at the top of Form 1120-X. For details and

special rules for an ESBC, see the Instructions for Form

3800.

Instructions for Form 1120-X (Rev. 12-2025) Catalog Number 95888A

Department of the Treasury Internal Revenue Service www.irs.gov

Information on Income, Deductions,

Tax Computation, etc.

For information on income, deductions, tax computation,

etc., see the instructions for the tax return for the tax year

being amended.

Deductions for such items as charitable contributions

and the dividends-received deduction may have to be

refigured because of changes made to items of income or

expense.

Where To File

File this form at the applicable Internal Revenue Service

Center where the corporation filed its original return.

Specific Instructions

Tax Year

In the space above the employer identification number,

enter the ending month and year of the calendar or fiscal

year for the tax return being amended.

Address

If the post office does not deliver mail to the street address

and the corporation has a P.O. box, show the box number

instead.

If the corporation receives its mail in care of a third

party (such as an accountant or an attorney), enter on the

street address line “C/O” followed by the third party’s

name and street address or P.O. box.

Question A. Election Under Regulations Section

301.9100

Check the “Yes” box if you are filing this Form 1120-X to

make an election under Regulations section 301.9100.

Identify the election in the entry space.

Otherwise, check the “No” box.

Question B. Election Under Published Guidance

or Administrative Relief

Check the “Yes” box if you are filing this Form 1120-X to

make an election under any other published guidance or

administrative relief. Identify the election in the entry

space.

Otherwise, check the “No” box.

Column (a)

Enter the amounts from the corporation’s return as

originally filed or as it was later amended. If the return was

changed or audited by the IRS, enter the amounts as

adjusted.

Column (b)

Enter the net increase or net decrease for each line being

changed. Use parentheses around all amounts that are

decreases. Explain the increase or decrease in Part II.

Column (c)

Note: Amounts entered on lines 1 through 4 in column (c)

must equal the amounts that would be entered on the

2

applicable lines of the tax return if all adjustments and

corrections were taken into account.

Lines 1 and 2. Add the increase in column (b) to the

amount in column (a) or subtract the column (b) decrease

from column (a). Enter the result in column (c). For an item

that did not change, enter the amount from column (a) in

column (c).

Line 4. Figure the new amount of tax using the taxable

income in line 3, column (c). Use Form 1120, Schedule J

of the original return to make the necessary tax

computation.

Line 5e. Enter the amount of tax deposited with Form

7004, Application for Automatic Extension of Time To File

Certain Business Income Tax, Information, and Other

Returns.

Line 5g. Include on line 5g any write-in credits or

payments, such as the credit for tax on ozone-depleting

chemicals or backup withholding, or similar items.

Line 8. Enter the amount from the “Overpayment” line of

the original return, even if the corporation chose to credit

all or part of this amount to the next year’s estimated tax.

This amount must be considered in preparing Form

1120-X because any refund due from the original return

will be refunded separately (or credited to estimated tax)

from any additional refund claimed on Form 1120-X. If the

original return was changed by the IRS and the result was

an additional overpayment of tax, also include that amount

on line 8.

Line 10. Tax due. If the corporation has access to U.S.

banking services or electronic payment systems, it should

use direct deposit for any refunds and pay electronically

for any payments, whenever possible. Most businesses

can make tax payments, including estimated tax

payments, federal tax deposits, and paying a balance due

on your return, using Electronic Federal Tax Payment

System (EFTPS), IRS Direct Pay, or your IRS business tax

account. For more information about EFTPS or to enroll in

EFTPS, go to EFTPS.gov.

• For more information about IRS Direct Pay, go to

IRS.gov/Direct Pay.

• For more information about creating and accessing your

IRS business tax account, go to IRS.gov/

BusinessAccount.

• For more information about other payment options, go

to IRS.gov/Pay.

If the corporation does not use electronic funds

transfers, including the EFTPS, enclose a check with this

form and make it payable to the “United States Treasury.”

See IRS.gov/PayByMail for more information.

Line 11. Overpayment. If the corporation is entitled to a

refund larger than the amount claimed on the original

return, line 11 will show only the additional amount of

overpayment. This additional amount will be refunded

separately from the amount claimed on the original return.

The IRS will figure any interest due and include it in the

refund.

Line 12. Enter the amount, if any, to be applied to the

estimated tax for the next tax period. Also, enter that tax

period. No interest will be paid on this amount. The

Instructions for Form 1120-X (Rev. 12-2025)

election to apply part or all of the overpayment to the next

year’s estimated tax is irrevocable.

Who Must Sign

The return must be signed and dated by:

• The president, vice president, treasurer, assistant

treasurer, chief accounting officer; or

• Any other corporate officer (such as tax officer)

authorized to sign.

If a return is filed on behalf of a corporation by a

receiver, trustee, or assignee, the fiduciary must sign the

return, instead of the corporate officer. A return signed by

a receiver or trustee in bankruptcy on behalf of a

corporation must be filed with a copy of the order or

instructions of the court authorizing signing of the return.

If an employee of the corporation completes Form

1120-X, the paid preparer’s space should remain blank.

Anyone who prepares Form 1120-X but does not charge

the corporation should not complete that section.

Generally, anyone who is paid to prepare the return must

sign it and fill in the “Paid Preparer Use Only” area.

See the Instructions for Form 1120 for more

information.

Part II—Explanation of Changes

The IRS needs to know why you are filing Form 1120-X.

See the following examples.

• To correct a mathematical or reporting error.

Simple mistakes like a clerical error, a miscalculated

figure, or omitting income.

• To claim a missed tax deduction or credit. After

filing, a business might discover it overlooked eligible tax

deductions (like operating expenses or depreciation) or

credits, such as the research or development credit or the

employee retention credit. Amending the return allows the

business to claim these missed benefits and potentially

reduce its tax liability that could result in a refund.

• To adjust for an NOL or credit carryback. If a

corporation has a net operating loss or certain unused

Instructions for Form 1120-X (Rev. 12-2025)

credits, it may be able to carry them back to a prior tax

year to claim a refund. While a tentative refund claim

(Form 1139) is an option for certain carrybacks, Form

1120-X is used to make this adjustment for prior years.

• To change a previous accounting method or

election. In some cases, a corporation may be permitted

by the IRS to make a specific accounting election on an

amended return after the initial deadline.

Paperwork Reduction Act Notice. We ask for the

information on this form to carry out the Internal Revenue

laws of the United States. You are required to give us the

information. We need it to ensure that you are complying

with these laws and to allow us to figure and collect the

right amount of tax.

You are not required to provide the information

requested on a form that is subject to the Paperwork

Reduction Act unless the form displays a valid OMB

control number. Books or records relating to a form or its

instructions must be retained as long as their contents

may become material in the administration of any Internal

Revenue law. Generally, tax returns and return information

are confidential, as required by section 6103.

The time needed to complete and file this form will vary

depending on individual circumstances. The estimated

burden for business taxpayers filing this form is approved

under OMB control number 1545-0123 and is included in

the estimates shown in the instructions for their business

income tax return.

If you have comments concerning the accuracy of

these time estimates or suggestions for making this form

simpler, we would be happy to hear from you. You can

send us comments through IRS.gov/FormComments. Or

you can send your comments to the Internal Revenue

Service, Tax Forms and Publications, 1111 Constitution

Ave. NW, IR-6526, Washington, DC 20224. Do not send

the form to this address. Instead, see Where To File,

earlier.

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