S.C. Code Ann. § 63-17-3810: Registration to modify.

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 provided in subpart 1 if the order has not been registered. A petition for modification may be filed at the same time as a request for registration, or later. The pleading must specify the grounds for modification.