N.Y.C. Admin. Code § 11-2041: § 11-2041 Transitional provisions.

The taxes imposed under paragraph one of subdivision (a) of section 11-2040 of this subchapter shall be paid with respect to receipts from all sales of services on or after September first, nineteen hundred seventy-five although rendered or agreed to be rendered under a prior contract. Where a service is sold on a monthly, quarterly, yearly or other term basis, the charge for such service shall be subject to tax under this subchapter to the extent that such charge is applicable to any period on or after September first, nineteen hundred seventy-five, and such charge shall be apportioned on the basis of the ratio of the number of days falling within such period to the total number of days in the full term or period.