N.J. Stat. § 43:13-22.59b
A member may file a detailed statement of public employment with a public employer in this State which was eligible for credit in a State-administered retirement system, or of military service in the Armed Forces of the United States, rendered prior to becoming a member, for which the member desires credit, and of such other facts as the retirement system may require. The member may purchase credit for all or a portion of the service evidenced in the statement up to the nearest number of years and months, but not exceeding three years. No application shall be accepted for the purchase of credit for the service if, at the time of application, the member has a vested right to retirement benefits in another retirement system based in whole or in part upon that service. A member who applies to purchase credit for such service shall pay the full cost attributable to the increased benefits to be derived from the purchased credit in accordance with the actuarial method used to determine the cost at the time of the purchase. The purchase may be made in a lump sum or in regular installments, equal to at least 1/2 of the full normal contribution to the retirement system, over a maximum period of 10 years. A member shall not be liable for any costs associated with the financing of pension adjustment benefits and health care benefits for retirees when purchasing credit.
Any member electing to make a purchase pursuant to this section who retires prior to completing payments as agreed with the retirement system will receive pro rata credit for the purchase prior to the date of retirement, but if the member so elects at the time of retirement, the member may make the additional lump sum payment required at that time to provide full credit.
N.J.S. § 43:13-22.59b