The commission shall give at least ten (10) days' written notice of the time and place of hearing and of the issues to be heard, either by personal service or by registered or certified mail. Service by mail shall be deemed complete when a copy of such notice is deposited in the United States post office, with postage prepaid, addressed to a party at his last known address, as shown in the records and files of the commission. Evidence of service by certificate or affidavit of the person making the same shall be filed with the commission.
Idaho Code § 72-713