N.Y. Tax Law § 615
(b) Husband and wife.
(c) Modifications reducing federal itemized deductions. The total amount of deductions from federal adjusted gross income shall be reduced by the amount of such federal deductions for:
(6) in the case of a shareholder of an S corporation
(d) Modifications increasing federal itemized deductions. The total amount of deductions from federal adjusted gross income shall be increased by:
(f) Except as provided under subsection (g) of this section, the New York itemized deduction otherwise allowable under this section shall be reduced by the sum of the amounts determined under paragraphs one and two of this subsection.
(1) An amount equal to the New York itemized deduction otherwise allowable under subsection (a) of this section, multiplied by a percentage, such percentage to be determined by multiplying, for taxable years beginning in nineteen hundred eighty-eight, ten percent, and for taxable years beginning after nineteen hundred eighty-eight, twenty-five percent, by a fraction,