D.C. Mun. Regs. tit. 10, r. 10-B3004
Any owner desiring a person to appear before or transact business with the Board. as agent of the owner, shall furnish the Board with his or her written authorization for that person to appear as his or her agent.
The signature of an attorney who is a member of the Bar of the District of Columbia, or a real estate broker who is licensed in the District, shall be sufficient to comply with the requirements of this section.
Forms for persons other than attorneys or real estate brokers shall be supplied by the Board.
Where two (2) or more ,persons have been authorized to appear before or transact business with the Board as agents for the same owner, service upon either one (1) of the agents shall constitute service upon the owner unless the owner has filed with the Board a designation of the agent to receive service, in which case service shall be upon the agent so designated.
Any person who has been authorized to act as agent for an owner in a case shall be deemed to continue to represent the owner until a notice of withdrawal of authority for representation signed by the agent or by the owner, together with proof of service of that notice upon the agent or owner. Forms for this purpose shall be furnished by the Board.
D.C. Mun. Regs. tit. 10, r. 10-B3004