S.C. Code § 9-8-70
Until the first payment of a retirement allowance becomes normally due, a member may elect, by filing written application with the board, to convert the retirement allowance otherwise payable on his account after retirement into a retirement allowance of equivalent actuarial value under which a reduced retirement allowance is payable during the beneficiary's life, with the provision that one-third of the reduced allowance continues after his death to and for the life of the contingent beneficiary designated by him in the application, if the beneficiary were to survive him. For purposes of this section, the member may not designate his spouse as contingent beneficiary.
Until the final payment of a retirement allowance becomes normally due, a member may elect, by filing written application with the board, to convert the retirement allowance otherwise payable on his account after retirement into a retirement allowance of equivalent actuarial value under which a reduced retirement allowance is payable during the beneficiary's life, with the provision that one-third of the reduced allowance is payable in equal shares to and for the life of each of two or more beneficiaries or to the trustee or trustees of the beneficiaries, for so long as each beneficiary survives him. The benefit reduction factor must be based on the average age of the beneficiaries.
The board may approve a five-year, pay-out plan developed by the actuary on the basis of the total retirement allowance for surviving beneficiaries, other than a spouse.
Except as provided in this section, a retired member may not change the form of his monthly payment after the first payment of a retirement allowance is due.
S.C. Code § 9-8-70