N.Y. General City Model Law § 27
The term "net income" means the gross income of a taxpayer less the deductions allowed by this subpart.
The net income shall be computed in accordance with the method of accounting regularly employed in keeping the books of such taxpayer; but if no such method of accounting has been so employed, or if the method employed does not clearly reflect the income, the computation shall be made upon such basis and in such manner as in the opinion of the director of finance does clearly reflect the income. In determining net income, war losses, taxation of property recovered, and basis of property shall be treated in substantially the same manner as such losses, recoveries and basis are treated under the applicable provisions of section thirteen hundred thirty-one of the internal revenue code.
N.Y. General City Model Law § 27