Tenn. Code Ann. § 8-36-303: Setting of retirement date

(a) Any member eligible to retire may set the effective date of the member's retirement at any date within one hundred fifty (150) days before or after the date the member's application is filed with the board; provided, that such effective date of retirement follows the date of such member's separation from service and that the member at the time so specified for the member's retirement shall have completed the applicable eligibility requirements as hereinabove set forth.

(b) A member may submit only one (1) retirement application even if the member has service credit in one (1) or more of the four (4) defined benefit plans administered by the retirement system pursuant to chapters 34-37 of this title. The retirement payment plan and beneficiary selected by the member on the retirement application shall be the same for all of the plans and may not be changed or revoked, except as provided in part 6 of this chapter. The retirement system shall pay benefits from each of the applicable plans on the member's effective date of retirement; provided, that the member has met the eligibility requirements of the particular plan for a retirement allowance. If on a member's effective date of retirement the member has not met the eligibility requirements for a retirement allowance from a particular plan, the retirement system shall commence payments from that plan once the member meets the eligibility requirements of the plan.