Tennessee Code Title 8. Public Officers and Employees § 8-36-606

(a) A retired member who has not selected an optional retirement allowance under § 8-36-601(b) may change the retiree's designated beneficiary at any time;  provided, that the change is in writing, duly executed and filed with the retirement system.

(b) The election of a designated beneficiary under an optional retirement allowance as provided in § 8-36-601(b) must not be canceled or changed by the retiree after the retiree's effective date of retirement except as provided in subsections (c)-(f).

(c) After a retired member's effective date of retirement or such later time as may be provided in rules adopted by the board of trustees, the retiree may cancel the retiree's designated beneficiary because of the death of the beneficiary or the retiree's divorce from the designated beneficiary, upon the written request of the retiree.  If the retiree designated multiple beneficiaries, then the portion of the benefit payment that was payable to the cancelled beneficiary must not be distributed or redistributed to the remaining beneficiaries.  The retiree shall provide the retirement system with the completed and signed written cancellation request accompanied by either of the following, whichever is applicable:

(d) If a retired member cancels the retiree's designated beneficiary pursuant to subsection (c), then the retiree may:

(e) If the retiree elects to reannuitize pursuant to subdivision (d)(2), then the retiree shall submit an application to reannuitize to the retirement system after the retired member's marriage to the proposed new beneficiary, and provide the retirement system with the marriage certificate demonstrating the marriage between the retiree and the proposed new beneficiary.

(f) Upon receiving a completed application, the retirement system shall process the reannuitization of the retiree's retirement benefit pursuant to the option selected by the retiree on the retiree's effective date of retirement.  The value of the new joint and survivor annuity must be the actuarial equivalent of the retiree's benefit prospectively, in effect at the time the new annuity is elected.  The benefit must be reduced based on the ages of the retiree and the new beneficiary at the time of the change.  The change in beneficiary must become effective in the month following the month that the retirement system approves the change in beneficiary.