Va. Code § 63.2-1917
In any subsequent child support enforcement proceeding between the parties, upon sufficient showing that diligent effort was made to ascertain the location of a party, that party may be served with any required notice by delivery of the written notice to that party's residential or business address as filed with the court pursuant to § 20-60.3 or the Department, or if changed, as shown in the records of the Department or the court or by electronic means as defined in § 63.2-1900. However, any person served with notice as provided in this section may challenge, in a subsequent judicial proceeding, an order entered based upon such service on the grounds that he did not receive the notice and enforcement of the order would constitute manifest injustice.
Va. Code § 63.2-1917