Tenn. Code Ann. § 8-34-621: Part-time, seasonal, retired or temporary employee service credit

(a) Any member or retired member may establish retirement credit for service rendered as a part-time employee upon making application therefor to the board of trustees. If such service is claimed within one (1) year of the member's date of membership or July 1, 1984, whichever is later, the member may establish retirement credit for service rendered as a part-time employee which has not been previously refunded, upon a payment of back contributions.

(b) Any state employee who is a member of the retirement system may establish retirement credit for service rendered as a seasonal or temporary employee upon making application therefor to the board of trustees. If such service is claimed within one (1) year of the member's date of membership or July 1, 1985, whichever is later, the member may establish retirement credit for such service which has not been previously refunded upon a payment of back contributions.

(c) If service is not established within the time specified in subsection (a) or (b) or if a member or retired member has been refunded for such service, then it may be established upon a payment of back contributions plus interest.

(d) A member or retired member establishing retirement credit under this section must establish credit for all service which is creditable under this system.