(a) In any proceeding to establish a child support order, in cases where the agency is not yet enforcing an order of support for the subject child, service of the notice provided in section 576E-5 shall be by personal service or certified mail, return receipt requested. In the case where the person to be served cannot be found, service shall be completed by leaving copies of the notice at the person's usual place of residence with some person of suitable age and discretion residing at that location. After initial service is effected, additional service upon a party shall be satisfied by regular mail to the party's last known address.(b) Service of the notice of hearing pursuant to the request for hearing under section 576E-6 of a party shall be satisfied by regular mail to the party's address provided with the request for hearing, or if not provided, to the party's last known address.(c) In any child support enforcement proceeding subsequent to an order already being enforced by the agency, upon a showing that diligent effort has been made to ascertain the location of a party, notice and service of process shall be presumed to be satisfied upon delivery of written notice to the most recent residential or employer address on file with the state case registry pursuant to section 571-52.6.L 1988, c 154, pt of §2; am L 1990, c 176, §11; am L 1994, c 105, §5; am L 1997, c 293, §34; am L 2001, c 95, §§ 5, 6§§5, 6; am L 2002, c 84, §7 .