29 CFR § 1955.15 - Manner of service and filing.

(a) Service of any document upon any party may be made by personal delivery of, or by mailing a copy of the document by certified mail, to the last known address of the party or his representative. The person serving the document shall certify to the manner and date of service.

(b) In addition to serving a copy of any documents upon the parties, the original and two copies of each document shall be filed with the administrative law judge. With respect to exhibits and transcripts, only originals or certified copies need be filed.