27 Miss. Code. R. 210-32-101
Political subdivisions may elect to join PERS and provide membership to their employees on a prospective basis only or they can also provide for retroactive service credit. If the political subdivision elects to provide service credit retroactive to a certain date, no credit for such service can be granted to a member until he or she has contributed to PERS under Article III beginning at Miss. Code. Ann. § 25-11-101, et seq. (1972, as amended) for the minimum required period based on the date of membership into the system and the appropriate cost for such service has been paid. Employees who became members of the retirement system before July 1, 2007, must have remained contributors to the system for a minimum of four (4) years, while employees who became members of the retirement system on or after July 1, 2007, must have remained contributors to the system for a minimum of eight (8) years, to be able to establish retroactive service credit.
The cost of such retroactive service prior to July 1, 1998, shall be controlled by the regulation, statutes and the addendum to the joinder agreement in effect at the time.
Effective July 1, 1998, no credit shall be granted for retroactive services between January 1, 1953, and the date of entry into the retirement system unless the member:
27 Miss. Code. R. 210-32-101