Idaho Code § 5-518
Service of process in an action to establish or enforce a support obligation may be made in the manner prescribed for service of process in a civil action by a duly authorized process server, or by certified mail, return receipt requested. Any uninterested party over the age of eighteen (18) including, but not necessarily limited to, employees of the bureau of child support enforcement and employees of the county prosecuting attorney's office, may serve such process. For the purposes of this section, service by mail shall be completed upon the obligor's receipt of such certified mail. The party or attorney making service by certified mail shall make a return certificate indicating that he complied with the provisions of this statute and attaching a receipt of the mailing signed by the obligor.
Idaho Code § 5-518