S.C. Code Ann. § 12-39-210

The auditor shall, at any time after making his return, if he ascertain that any personal property in his county has not been listed, list it and make return thereof, with the valuation thereof as fixed by the owner or himself and the name of the owner or person to whom it is taxable, and he shall charge it on the duplicate for taxation, adding ten per cent to the value as returned as penalty.