O.C.G.A. § 19-11-168

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 Georgia in the same manner provided in 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 later. The pleading must specify the grounds for modification.