N.Y.C. Admin. Code § 13-248: § 13-248 Retirement; selection of age fifty-five.

Any person becoming a member who was not previously a member or who during his or her last previous membership in the pension fund contributed on the basis of a minimum retirement age of fifty-five, may elect, prior to the certification of his or her rate of contribution, to contribute on the basis of a minimum retirement age of fifty-five by a written election duly executed and acknowledged and filed with the board. The minimum age of retirement for such members so electing shall be fifty-five years, and all contributions and benefits payable by or on account of such member shall be computed on the basis of such minimum retirement age.