S.C. Code § 9-1-1850
A member who has at least twenty-five years of creditable service may elect to receive up to three years of additional service credit as though the additional service credit were rendered by the member as an employee or member upon paying into the member's retirement system, during the ensuing number of years the member wishes to purchase in the manner the Comptroller General shall direct, the employer and employee contributions that would be due for the position that the member presently holds at the salary level in effect during those years. If the position is consolidated or eliminated after the member's retirement, the member shall pay the employer and employee contributions during the remaining required years at a level equal to what these contributions were for the position before its consolidation or elimination. The member also shall pay the employer and employee cost for health and dental insurance in effect during the ensuing years the member wishes to purchase. The additional service credit qualifies the member for retirement and the member must terminate employment within ninety days after electing the option provided by this section. The salary level of the position the member presently holds, during the ensuing years the member pays the employer and employee contributions, is attributable to the member for purposes of determining the member's average final compensation.
The retirement benefits of the member shall not commence until the time benefits would have been paid when the member had completed twenty-eight years of service.
The option allowed by this section cannot be exercised if the member has purchased nonqualified service pursuant to Section 9-1-1140(E).
S.C. Code § 9-1-1850