(a) Service of documents under this part shall be made by delivery to the person, an officer of a corporation, or attorney of record, or by mailing the document to the last known address of the person, officer, or attorney. If service is made by mail, it shall be considered complete upon mailing. Unless otherwise provided in this subpart, service need not be made by certified mail. If service is made by delivery, it shall be considered complete upon actual receipt by the person, officer, or attorney; upon leaving it at the person's, officer's or attorney's office with a clerk or person in charge; upon leaving it at a conspicuous place in the office if no one is in charge; or by leaving it at the person's or attorney's residence.

(b) If a complaint has been filed pursuant to §726.309, two copies of all documents filed in any administrative proceeding under this subpart shall be served on the attorneys for the Department of Labor. One copy shall be served on the Associate Solicitor, Black Lung Benefits Division, Room N-2117, Office of the Solicitor, U.S. Department of Labor, 200 Constitution Ave., NW., Washington, DC 20210, and one copy on the attorney representing the Department in the proceeding.

(c) The time allowed a party to file any response under this subpart shall be computed beginning with the day following the action requiring a response, and shall include the last day of the period, unless it is a Saturday, Sunday, or federally-observed holiday, see §725.311 of Part 725 of this subchapter, in which case the time period shall include the next business day.