D.C. Mun. Regs. tit. 14, r. 14-3911
All petitions and other documents required to be served upon any person under this chapter shall be served upon that person or the representative designated by a party, as provided in § 3918, in the manner provided in this section. All petitions and applications under Chapter 42 of this title shall be served on affected parties by the Rent Administrator or Office of Administrative Hearings after they are filed, unless otherwise specified by that chapter.
When a party has a representative of record after a proceeding has been initiated, as provided in § 3918, service shall be made upon the representative.
Notwithstanding § 904(a) of the Act (D.C. Official Code § 42-3509.04(a)) , service upon any person or representative shall be completed only:
Actual receipt of service shall bar any claim of defective service, except for a claim with respect to the timeliness of service.
Service by mail of the U.S. Postal Service shall be complete upon mailing.
All petitions or other documents required to be served on the other party or parties shall be served prior to or at the same time as they are filed with the Rental Accommodations Division.
Every pleading, motion, and other document filed with the Rental Accommodations Division shall include a signed statement that it was served as required, which shall be captioned as a "certificate of service" and shall show the date, name of the person(s) served, address at which service was made, and the manner of service. If service is made by a process server, proof of service shall be in an affidavit showing the date, the person served, address at which service was made, the manner of service, and the name and address of the process server.
D.C. Mun. Regs. tit. 14, r. 14-3911