S.C. Code Ann. § 9-1-1020
The employee annuity savings fund shall be the account in which shall be recorded the contributions deducted from the earnable compensation of members to provide for their employee annuities. Each employer shall cause to be deducted from the compensation of each member on each and every payroll of such employer for each and every payroll period four percent of his earnable compensation. With respect to each member who is eligible for coverage under the Social Security Act in accordance with the agreement entered into during 1955 in accordance with the provisions of Chapter 7 of this Title; however, such deduction shall, commencing with the first day of the period of service with respect to which such agreement is effective, be at the rate of three percent of the part of his earnable compensation not in excess of four thousand eight hundred dollars, plus five percent of the part of his earnable compensation in excess of four thousand eight hundred dollars. In the case of any member so eligible and receiving compensation from two or more employers, such deductions may be adjusted under such rules as the Board may establish so as to be as nearly equivalent as practicable to the deductions which would have been made had the member received all of such compensation from one employer. In determining the amount earnable by a member in a payroll period, the Board may consider the rate of annual earnable compensation of such member on the first day of the payroll period as continuing throughout such payroll period and it may omit deduction from earnable compensation for any period less than a full payroll period if a teacher or employee was not a member on the first day of the payroll period.
Each employer shall certify to the Board on each and every payroll or in such other manner as the Board may prescribe the amounts to be deducted and such amounts shall be deducted and, when deducted, shall be credited to said employee annuity savings fund, to the individual accounts of the members from whose compensation the deductions were made.
The rates of the deductions must be, without regard to a member's coverage under the Social Security Act, as follows: in the case of Class One members, five percent of earnable compensation and, in the case of Class Two members, six percent of earnable compensation.
Each department and political subdivision shall pick up the employee contributions required by this section for all compensation paid on or after July 1, 1982, and the contributions so picked up shall be treated as employer contributions in determining federal tax treatment under the United States Internal Revenue Code; however, each department and political subdivision shall continue to withhold federal income taxes based upon these contributions until the Internal Revenue Service, or the federal courts, rule that, pursuant to Section 414(h) of the United States Internal Revenue Code, these contributions shall not be included as gross income of the employee until such time as they are distributed or made available. The department and political subdivision shall pay these employee contributions from the same source of funds which is used in paying earnings to the employee. The department and political subdivision may pick up these contributions by a reduction in the cash salary of the employee. Employee contributions picked up shall be treated for all purposes of this section in the same manner and to the extent as employee contributions made prior to the date picked up.
Payments for unused sick leave, single special payments at retirement, bonus and incentive-type payments, or any other payments not considered a part of the regular salary base are not compensation for which contributions are deductible. Contributions are deductible on pay for unused annual leave.