45 CFR § 1149.43 - How are documents filed and served with the ALJ?
(a) Documents are considered filed when they are mailed. The date of mailing may be established by a certificate from the party or his/her representative, or by proof that the document was sent by certified or registered mail.
(b) A party filing a document with the ALJ must, at the time of filing, serve a copy of such document on every other party. When a party is represented by a representative, the party's representative must be served in lieu of the party.
(c) A certificate of the individual serving the document by personal delivery or mail and setting forth the manner of service will be proof of service.
(d) Service upon any party of any document other than the complaint must be made by delivering a copy or by placing a copy in the United States mail, postage prepaid and addressed to the party's last known address.
(e) If a party consents in writing, documents may be sent electronically. In this instance, service is complete upon transmission unless the serving party receives electronic notification that transmission of the communication was not completed.