Tenn. Code Ann. § 8-36-905

Any participant who desires to establish service credit pursuant to chapters 34-37 of this title shall pay employee contributions to the defined benefit component of the plan equal to the amount of the employee contributions required under the terms of the hybrid plan as they existed at the time the service was established, plus interest at the rate provided in § 8-37-214. In the case of refunded service, the amount shall be equal to the total amount that was previously withdrawn, plus interest at the rate provided in § 8-37-124. Any service established or reestablished pursuant to this section shall be credited under the terms of the hybrid plan as they existed at the time the service was established and not at the time the service was rendered.