S.C. Code Ann. § 63-17-3070 – Multiple tribunals

(A) If a proceeding is brought under this article and only one tribunal has issued a child-support order, the order of that tribunal controls and must be so recognized.
(B) If a proceeding is brought under this article, and two or more child-support orders have been issued by tribunals of this State or another state with regard to the same obligor and same child, a tribunal of this State having personal jurisdiction over both the obligor and individual obligee shall apply the following rules and by order shall determine which order controls:
1. (1) If only one of the tribunals would have continuing, exclusive jurisdiction under this article, the order of that tribunal controls and must be so recognized.
2. (2) If more than one of the tribunals would have continuing, exclusive jurisdiction under this article:
  1. (a) an order issued by a tribunal in the current home state of the child controls; but
  2. (b) if an order has not been issued in the current home state of the child, the order most recently issued controls.
3. (3) If none of the tribunals would have continuing, exclusive jurisdiction under this article, the tribunal of this State shall issue a child-support order, which controls.
(C) If two or more child-support orders have been issued for the same obligor and same child, upon request of a party who is an individual or a support enforcement agency, a tribunal of this State having personal jurisdiction over both the obligor and the obligee who is an individual shall determine which order controls under subsection (B). The request may be filed with a registration for enforcement or registration for modification pursuant to Part VI, or may be filed as a separate proceeding.
(D) A request to determine which is the controlling order must be accompanied by a copy of every child-support order in effect and the applicable record of payments. The requesting party shall give notice of the request to each party whose rights may be affected by the determination.
(E) The tribunal that issued the controlling order under subsection (A), (B), or (C) has continuing jurisdiction to the extent provided in Section 63-17-3050 or 63-17-3060.
(F) A tribunal of this State that determines by order which is the controlling order under subsection (B)(1) or (2) or (C), or that issues a new controlling order under subsection (B)(3), shall state in that order:
1. (1) the basis upon which the tribunal made its determination;
2. (2) the amount of prospective support, if any; and
3. (3) the total amount of consolidated arrears and accrued interest, if any, under all of the orders after all payments made are credited as provided by Section 63-17-3090.
(G) Within thirty days after issuance of an order determining which is the controlling order, the party obtaining the order shall file a certified copy of it in each tribunal that issued or registered an earlier order of child support. A party or support enforcement agency obtaining the order that fails to file a certified copy is subject to appropriate sanctions by a tribunal in which the issue of failure to file arises. The failure to file does not affect the validity or enforceability of the controlling order.
(H) An order that has been determined to be the controlling order, or a judgment for consolidated arrears of support and interest, if any, made pursuant to this section must be recognized in proceedings under this article.