S.C. Code Ann. § 44-7-660

In order to meet the principal and interest of such bonds as they mature, the auditor of the county or the clerk of the council of any town or city shall annually levy upon all of the property of such county, township, city or town taxes not exceeding two mills and for a period of time not exceeding twenty years, the proceeds from such levy to be paid out by the proper officers for the retirement of the principal and interest on any bonds sold.