S.C. Code Ann. § 20-7-1148
A party or support enforcement agency seeking to modify or to modify and enforce a child support order issued in another state shall register that order in this State in the same manner as provided in Sections 20-7-1132 through 20-7-1138. A complaint setting forth the grounds for modification with specificity may be filed at the same time as a request for registration and enforcement or at a later time.