Tax Law, § 612 (f)
Where a husband and wife determine their Federal income tax for a particular taxable year on a joint Federal income tax return, but are required to determine their New York State personal income taxes separately, they are then required to compute their New York adjusted gross incomes separately; that is, in the same manner as if the Federal adjusted gross income of each spouse had been determined on separate Federal income tax returns filed by them. Several of the various special situations arising from these different methods of filing income tax returns under the two laws are discussed in this section.
Where a husband and wife file a joint Federal income tax return, but are required to file separate New York State personal income tax returns, the individual retirement arrangement deduction allowable on the separate New York State personal income tax return of each spouse is the amount of such deduction which would be allowable if a separate Federal income tax return had been filed by each spouse for the taxable year involved (see section 219 of the Internal Revenue Code).
A net operating loss carryback or carryover results in a recomputation of Federal adjusted gross income for the prior or succeeding years. Such net operating loss carryback or carryover is, therefore, reflected in New York adjusted gross income for the taxable year involved. Where a husband and wife are required to file separate New York State personal income tax returns, the benefit of the net operating loss carryback or carryover may be claimed only by the spouse who sustained the loss.
A husband and wife who file a joint Federal income tax return and who are required to file separate New York State personal income tax returns must each report his or her share of income from jointly owned real estate, stocks, bonds, bank accounts and other property, in the same manner as if their Federal adjusted gross incomes had been determined separately. The rules for determining the manner of reporting this income depend upon the nature of the ownership interests and, in general, may be summarized as follows:
Example:
H and W file a joint Federal income tax return, including therein H's short-term capital gain of $10,000 and W's short-term capital loss of $9,000. On their joint Federal income tax return, a net short-term capital gain of $1,000 would be reportable and there would be no capital loss carryover for Federal income tax purposes, regardless of whether H and W file a joint or separate Federal income tax return in the subsequent taxable year. On their separate New York State personal income tax returns, H would include his capital gain of $10,000 and W would report a capital loss which would be limited to the maximum amount of capital loss allowed a married individual filing a separate Federal income tax return. W would not be allowed a capital loss carryover on her subsequent New York State personal income tax return since she cannot claim a capital loss carryover on her subsequent Federal income tax return whether a joint or separate Federal income tax return is filed.
N.Y. Comp. Codes R. & Regs. Tit. 20 § 112.6