New York Consolidated Laws, General City Law - GCT § 51. Requirement of withholding tax from wages

(a) General.  On or after the first payroll period beginning forty-five days after the date this local law becomes effective, every employer maintaining an office or transacting business within this state and making payment of any wages taxable under this local law shall deduct and withhold from such wages for each payroll period a tax computed in such manner as to result, so far as practicable, in withholding from the employee's wages during each calendar year an amount substantially equivalent to the tax reasonably estimated to be due under this local law resulting from the inclusion in the employee's city adjusted gross income of his wages received during such calendar year.  The method of determining the amount to be withheld shall be prescribed by regulations of the administrator with due regard to the city withholding exemptions of the employee and the sum of any credits allowable against his tax.  This section shall not apply to payments by the United States for service in the armed forces of the United States.

(b) Withholding exemptions.  For purposes of this section: