S.C. Code Regs. § § 19-984
An active contributing member is eligible to transfer all or any part of service credited, or which could have been credited, under another State Retirement System. A member is authorized to make only one such transfer, except that a member at employment termination, who does not qualify for a benefit under the Judicial-Solicitor Retirement System, may transfer credit back to the appropriate system.
Duplicate service credit under the same system is not permitted. A member shall not receive more than 1 year service credit during a twelve month period under one retirement system.
Service credit transfers from the General Assembly Retirement System (GARS) shall be included and counted in the total under the 22 year maximum service credit provision of Section 9-9-60 of the 1976 Code of Laws. Once a service credit transfer from the GARS is made, a member may not then make a contribution to re-establish that credit in the GARS.
S.C. Code Regs. § 19-984