S.C. Code Ann. § 9-1-1670

(A) If a change or error in the records results in a member or beneficiary receiving from the system more or less than he would have been entitled to receive had the records been correct, the board shall correct the error and, so far as practicable, adjust the payment so that the actuarial equivalent of the benefit to which the member or beneficiary was correctly entitled is paid. (B) The system must correct its records relating to a member upon: (1) written certification from the employer that the employer's records contained an error that affected the enrollment of the member; and (2) a showing to the system that all other related records and accounts have been corrected and adjusted to correspond to the change requested of the system. A correction of the records of the system takes effect only upon payment by the employer and employee to the system of costs as determined by the system. (C) An employer's request to correct a member's record pursuant to subsection (B) must be made within two years of the commission of the error by the employer.