S.C. Code § 12-37-810
The county auditor, when he shall deem it necessary, may adjourn the examination provided for in Section 12-37-780 from time to time, and if he shall find that the person examined has intentionally made a false return or returned his property for taxation at less than its fair cash value, he shall determine what amount should have been returned by such person and add ten per cent thereto as penalty and charge such property, with such penalty, against such person on the duplicate, with the taxes of the current year and the taxes of each preceding year it may have escaped taxation, with twenty per cent penalties upon such taxes of preceding years. But if he shall find the party committed merely an unintentional mistake in his return, he shall add such amount as he may deem just to such return and charge the person with the simple taxes thereon.
S.C. Code § 12-37-810