§ 637. Computation of separate tax on the ordinary income portion of lump sum distributions received by nonresident or part-year resident individuals, estates and trusts. (a) General. The tax imposed under section six hundred three for any taxable year, with respect to the ordinary income portion of a lump sum distribution received by a nonresident or part-year resident individual, estate or trust shall be applicable to the ordinary income portion of a lump sum distribution wholly or partly derived from or connected with New York sources, and the amount of such tax shall be computed in the same manner as that set forth in section six hundred twenty-four, except that if the lump sum distribution was partly derived from or connected with New York sources, the total taxable amount and the ordinary income portion of the lump sum distribution referred to in such section shall be determined by apportionment and allocation, pursuant to regulations promulgated by the state tax commission.

(b) Special rule for part-year residents. In the case of a part-year resident, the ordinary income portion of a lump sum distribution wholly or partly derived from or connected with New York sources shall be the sum of:

(1) The ordinary income portion of a lump sum distribution for the period of residence, computed as if the taxable year for federal income tax purposes were limited to the period of residence.

(2) The ordinary income portion of a lump sum distribution for the period of nonresidence, determined in accordance with subsection (a) of this section, computed as if the taxable year for federal income tax purposes were limited to the period of nonresidence.