O.C.G.A. § 19-11-175

A party or support enforcement agency seeking to modify, or to modify and enforce, a foreign child support order not under the convention may register that order in this state under Code Sections 19-11-160 through 19-11-167 if the order has not been registered. A petition for modification may be filed at the same time as a request for registration, or at another time. The petition must specify the grounds for modification.