S.C. Code Ann. § 8-11-940
(A) Performance increases must be based upon performance appraisals containing the following categories:
(4) substantially exceeds performance requirements - four percent increase.
The dollar amount of each performance increase must be added to the employee's base pay until the pay level of the employee has reached the maximum of his grade or executive compensation level. After the employee has reached maximum pay in his grade or executive compensation level, he may continue to receive performance pay but it must not be added to the base pay.