Okla. Admin. Code § 715:10-15-10.1
If the designated joint annuitant under the Option 2 or 3 retirement plan dies at any time after the member's retirement date, but before the death of the member, the member shall return to the retirement benefit, including any postretirement benefit increases the member would have received had the member not selected the Option 2 or 3 retirement plan. In such an event, the member's monthly retirement benefit and any amount due at the death of the member shall be calculated as if the member had selected the Maximum retirement allowance. The increase in the member's monthly benefit becomes effective the first day of the month following the date of death of the designated joint annuitant and shall be payable for the member's remaining lifetime. The member shall notify TRS of the death of the designated joint annuitant in writing by providing a certified copy of the joint annuitant's death certificate. If the joint annuitant's death certificate has not yet been issued by the Medical Examiner, or for other good cause shown, the Executive Director of TRS may accept alternative documentation to establish proof of death for purposes of this section. In the absence of timely notice, TRS shall make retroactive benefit payments to the member, not to exceed six (6) months from the time the member first became eligible for increased benefits to the date notification is received. Notwithstanding any other provision, increased benefits will not be due for any period prior to July 1, 1994.
Okla. Admin. Code § 715:10-15-10.1