Section 5.309 - Proof of service(a) The person serving a subpoena shall make a written statement setting forth the date, time and manner of service and shall return such report with or on a copy of the subpoena to the investigating officer or Administrative Law Judge who issued it. In case of failure to make service of a subpoena, the person assigned to serve such subpoena shall make a written statement setting forth the reasons the subpoena was not served. The statement should be placed on the subpoena or attached to it and returned to the investigating office or Administrative Law Judge who issued the subpoena.(b) When service of a subpoena is made by certified mail with return receipt to be signed by the addressee only, the person mailing the subpoena shall make a written statement on a copy of the subpoena or attached to it, setting forth the date, time and location of the post office where mailed, the post office number assigned thereto. If delivered, the receipt requested shall be returned, by the person receiving the receipt, to the investigating officer or Administrative Law Judge who issued the subpoena. In case the subpoena is not delivered, any information reported by the post office regarding non-delivery shall be given to the investigating officer or Administrative Law Judge who issued the subpoena.