The opinion
Kaplan, J.
(concurring). It would be quite in keeping with the modern, now accepted view of “claim,” “splitting” of a claim, and required consolidation of defenses, to hold that a taxpayer should be obliged to present in a single application all his available grounds for demanding abatement of the annual tax shown on his return, or of an assessment or additional assessment of annual tax, on pain otherwise of forgoing any such ground that he omits. I believe G. L. c. 63, §§ 51, 71, left room for the board to adopt this view, but the 1966 decisions, going on a somewhat different basis, were inconclusive, except perhaps as to abatement of additional assessment. One can say that the commission brought the present decision on itself by failing to promulgate a regulation that might inform taxpayers more clearly how they must proceed. It will perhaps occur to the commission that a procedural distinction between abatement of additional assessment and other abatements is not very satisfac *31 tory, and that the route of fashioning a well modulated regulation to govern future cases may still be open to it. See G. L. c. 14, § 4, cl. 1; c. 62G, § 3; see also c. 58A, § 8.