§ 635. Credit to trust beneficiary receiving accumulation distribution. A nonresident or part-year resident beneficiary of a trust whose New York source income includes all or part of an accumulation distribution by such trust, as defined in section six hundred sixty-five of the internal revenue code, shall be allowed a credit against the tax otherwise due under this article, computed in the same manner and subject to the same limitation as provided by section six hundred twenty-one with respect to a resident beneficiary except that such limitation shall be applied as if it also referred to an exclusion from New York source income.