N.Y. Comp. Codes R. & Regs. tit. 20 § 291.2
Every employer required to deduct and withhold New York City personal income tax on residents, pursuant to section 1309 of the Tax Law and section 11- 1771 of the Administrative Code of the City of New York, shall file an employer's return and with such return pay over to the Department of Taxation and Finance the amount of the New York City personal income tax so required to be deducted and withheld. An employer's return of New York City personal income tax withheld must be filed in the same manner as is provided for in Part 174 of this Title. However, in determining the threshold for filing such employer's return and making payment of withheld New York City personal income tax on residents, the amount of New York City personal income tax on residents required to be deducted and withheld shall be aggregated with the amounts of New York State personal income tax, New York City earnings tax on nonresidents, City of Yonkers income tax surcharge on residents and City of Yonkers earnings tax on nonresidents required to be deducted and withheld, and the total of all such withheld amounts determines the manner and timing of filing employer's returns and making payment of such withheld amounts.
N.Y. Comp. Codes R. & Regs. Tit. 20 § 291.2