Va. Code Ann. § 20-88.77:4

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 the Commonwealth under Article 8 (§ 20-88.66 et seq.) 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.