S.C. Code Ann. § 37-2-705

(1) With respect to a consumer rental-purchase agreement, the parties may contract for delinquency charges as follows: (a) For consumer rental-purchase agreements with payment or renewal dates which are monthly or less often than monthly, a delinquency charge not exceeding four dollars may be assessed on any payment not made within five business days after payment is due or return of the property is required. (b) For consumer rental-purchase agreements with payment or renewal date options to renew more frequently than monthly, a delinquency charge not exceeding two dollars may be assessed on any payment not made within three business days after payment is due or the return of the property is required. (2) A delinquency charge on a consumer rental-purchase agreement may be collected only once on any scheduled payment no matter how long it remains in default. A delinquency charge may be collected at the time it accrues or at any time thereafter. No delinquency charge may be assessed against a payment that is timely made even though an earlier delinquency charge has not been paid in full.