Tax Law, § 12(b) of § 1340(c); Codes and Ordinances of the City of Yonkers, § 92-109(b)
The City of Yonkers taxable wages and net earnings from self-employment of a taxpayer applicable to the portion of the year during which such taxpayer is a nonresident of the City of Yonkers must be determined, except as provided in section 266.3 of this Part, as if such taxpayer's taxable year for Federal income tax purposes were limited to the period of nonresident status.
N.Y. Comp. Codes R. & Regs. Tit. 20 § 266.2