Tenn. Code § 8-3435
Any member who has a prior service certificate in full force and effect, in addition to the deduction in § 8-3431, shall have deducted from his payroll compensation such portion or percentage as the board may designate, of his compensation for the next preceding payroll period of equal length of time as the current payroll period. Preceding payroll period for prior service shall begin with the last period a member was employed immediately before the member began to contribute to the retirement system, and shall proceed backward until all contributions for prior service have been made, or until withdrawal from the service, or until retirement, or until death of such member. Upon retirement of a member with prior service, where all contributions have not been made, there shall be deducted from each monthly retirement allowance of said member such portion or percentage as the board may designate of the compensation for the next preceding month for which contribution has not been made and such deductions shall continue until all contributions for prior service have been made, or until death; or in case of settlement by some other method as may be determined by the board, then the board shall determine the time of payment of any unpaid contributions. A member may elect to pay contributions for prior service in one (1) lump sum, or in more than one monthly payment.
T.C.A. § 8-3435