N.Y. Comp. Codes R. & Regs. tit. 21, § 5025.3 – Application for reinstatement of prior membership.

(a) A member may apply for reinstatement of a prior membership in a public retirement system by filing the form provided to such member by the system duly signed by the member and acknowledged by a notary public or, upon joining or rejoining the system, by completing the appropriate portion of a membership application filed with the system.
(b) Where a member is required to repay amounts previously refunded at the time such prior membership in a public retirement system ceased as a condition to reinstatement of such prior membership, such amounts, together with interest thereon, must be paid in a lump sum. Repayments of previously paid out benefits shall comply with section 415(k)(3) of the Internal Revenue Code and any Treasury Regulations thereunder.
(c) A member of this system subject to article 14 or 15 of the Retirement and Social Security Law may not obtain reinstatement of a prior membership not subject to either article unless and until such member shall have repaid in full any loan of the member’s accumulated contributions pursuant to either such article, as applicable.
(d) A member of this system shall be entitled to have a prior membership in a public retirement system reinstated, notwithstanding transfer of such membership to another public retirement system of the State, provided such membership shall have ceased following transfer by reason of insufficient service, withdrawal of accumulated contributions, or withdrawal of membership.
(e) No member of the system entitled to reinstatement of a prior membership in a public retirement system shall be entitled to credit for service rendered prior to the date the member last joined the system where the member is receiving a benefit or entitled to receive in the future a benefit from any public retirement system of the State or any other state for such service.
(f) A member who was retired from this system for service or with a deferred vested benefit shall be deemed a member, and not a retiree, of a public retirement system for the purposes of this Part only if the member shall have elected the provisions of paragraph b of subdivision 11 of section 503 of the Education Law. Upon reinstatement, however, any such member with an original date of membership prior to June 30, 1973 shall be entitled to all the rights, benefits and privileges to which such member would have been entitled, had the member entered into membership in the system on June 30, 1973.
(g) A member may apply for reinstatement of a prior membership date at retirement. In such event, the following procedure shall apply:
1. (1) the member shall be retired under his or her existing membership date unless or until he or she files a confirmation of his or her intention to be reinstated to a prior membership as provided in this Part;
2. (2) if the system determines based upon the information provided to it by the member or a review of the member’s file with the system that he or she is eligible for reinstatement, it shall so notify the member and he or she shall thereafter have 30 days within which to file a confirmation of his or her intention to be reinstated to a prior membership date;
3. (3) the member’s confirmation of his or her intention to be reinstated to a prior membership date shall be on a form provided to him or her by the system duly signed by him or her and acknowledged by a notary public; such confirmation upon filing with the system shall be irrevocable;
4. (4) the member’s right to confirm his or her intention to be reinstated to a prior membership date shall be extinguished on the occurrence of the earliest of:
  1. (i) his or her death;
  2. (ii) the expiration of the 30-day period from the notification of his or her eligibility for reinstatement; or
  3. (iii) the date on which his or her retirement benefit is finally determined (i.e., “final close-out”);
5. (5) this subdivision shall have no application to a member who has already been reinstated to a prior membership date or to a member who last joined on or after July 27, 1976 and whose loan pursuant to section 517(b) or 613(a) has not been repaid in full no later than 30 days following the member's effective date of retirement.