S.C. Code Ann. § 12-8-1050 — Withholding on wages paid for period which is not payroll period; withholding on wages paid without regard to any period; withholding in miscellaneous payroll period

(A) If wages are paid for a period which is not a payroll period, the amount to be withheld is that amount applicable to a miscellaneous payroll period containing the number of days, including Sundays and holidays, equal to the number of days in the period for which such wages are paid.
(B) If wages are paid by an employer without regard to a payroll period or other period, the amount to be withheld is that amount applicable to a miscellaneous payroll period containing the number of days, including Sundays and holidays, which have elapsed since the date of the last payment of such wages to the employee during the calendar year, the date of commencement of employment of the employee or January first, whichever is the later.
(C) To compute the withholding required in a miscellaneous payroll period, the daily payroll withholding tables published by the department must be used in the same manner as provided in Internal Revenue Code Subsections 3402(c)(2) and (c)(3).