Tenn. Code § 8-4012
All county officials, as herein defined, in office as of June 30, 1968, and thereafter, shall be eligible to participate as members of this retirement system, provided, however, in order to qualify as a member of this system, a county official shall be required to give notice in writing of his or her intentions to participate to the chairman of the retirement board within ninety (90) days from July 1, 1968 or July 1, 1972, if said county official is in office on that date, or within ninety (90) days from the date said county official is sworn into office, or becomes eligible to participate in the system. In the event the county official desires to be credited with the service as set forth in § 8-4001(f) hereof, said written notice of intention to the chairman of the retirement board shall be accompanied by a back-service contribution, which back-service contribution shall be an amount equal to three and one-half per cent (3 ½%) of the salary received by the county official who desires to qualify as a member of this system during the time of his service as set forth in § 8-4001(f) hereof and shall be accompanied by the appropriate contribution as hereinafter provided in § 8-4013, covering the period from July 1, 1968, to the date of said written notice, or the period from the date said county official is sworn into office to the date of said notice; provided further that any county official not making the back-service contribution set forth herein shall not be credited with the service as set forth in § 8-4001(f) hereof.
A county sheriff may file the written notice required by this section on or before July 1, 1971 or within ninety (90) days after he is sworn into office. Claim for credit in the retirement system for prior service for time served as sheriff must be made with the county officials' retirement board or secretary within ninety (90) days from May 26, 1971.
Any person who served continuously as a circuit court clerk for not less than twenty (20) years prior to the establishment of the Tennessee retirement system for county officials and whose service in such capacity ended not earlier than August 31, 1966, shall be entitled to the benefits provided by this chapter, upon written application to the retirement board on or before July 1, 1970, accompanied by such evidence of such prior service as may be satisfactory to the board, and by a lump sum payment of the back-service contributions as required by this section.
Any person who, on July 1, 1968, was a member of the Tennessee state retirement system as a member of the general assembly and who served not less than sixteen (16) years as a county court clerk is entitled to the benefits provided by this chapter and shall receive retirement credit in the system provided by this chapter for such time served as a county court clerk and as a member of the general assembly. Such funds as may be to his credit in the Tennessee state retirement system shall be transferred to the Tennessee retirement system for county officials upon application in writing to the retirement board established by this chapter, which shall in turn certify to the Tennessee state retirement board the request for transfer. The Tennessee state retirement board shall then cause such funds as are credited to the account of such person in the Tennessee state retirement system to be transferred to the retirement board established by this chapter. Such person shall accompany his request by such evidence of prior service as may be satisfactory to the board. If the amount of money such person would have contributed to the retirement system if it had been in effect for the number of years such person served as a county court clerk and as a member of the general assembly and if he had been a member of such system is more than the amount of money credited to his account in the Tennessee state retirement system's employees' fund, he shall be required to make a lump sum payment of the difference between such amounts to the board in order to complete the transfer. If the amount he would have contributed to the retirement system for such number of years is less than the amount credited to his account in the Tennessee state retirement system's employees' fund, he shall be reimbursed for the difference between such amounts by the board upon completion of the transfer.
Any county official who served as county chairman or delegate to a constitutional convention prior to becoming a member of this retirement system shall be entitled to credit for such service; provided that prior to July 1, 1971 he makes a written request to the retirement board for such credit, furnishes satisfactory evidence thereof, and pays into the retirement fund a back-service contribution in an amount equal to three and one-half per cent (3½%) of the salary received for such service.
T.C.A. § 8-4012