N.J. Stat. § 43:16A-11.4
If an employee who has withdrawn the accumulated member's contributions from the Police and Firemen's Retirement System, as provided by section 11 of P.L. 1944, c.255 (C.43:16A-11) is reenrolled as a member of the retirement system, the member may purchase credit for all of the previous membership service by paying into the annuity savings fund the amount required by applying the factor, supplied by the actuary as being applicable to the member's age at the time of the purchase, to the member's salary at that time, or the highest annual compensation for service in this State for which contributions shall have been made during any fiscal year of membership or to the highest annual compensation for service in this State during any fiscal year for which credit is purchased, whichever is the highest. The purchase may be made in regular installments, equal to at least 1/2 the normal contribution to the retirement system, over a maximum period of 10 years.
Any member electing to purchase service credit hereunder who retires prior to completing the payments as agreed with the retirement system will receive pro rata credit for service purchased 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. § 43:16A-11.4