D.C. Mun. Regs. tit. 18, r. 18-802
Any notice or order served under the authority of this chapter shall be properly served upon the person to whom the notice is directed if a copy of the notice or order is served upon him or her personally, or if a copy of the notice or order is mailed postage prepaid to the last known address of the person to be notified and the copy is not returned by the Postal Service authorities.
For the purpose of this chapter, with respect to any person licensed by the District to operate a motor vehicle or whose motor vehicle is registered in the District, the term "last known address" shall mean the most recent address shown on the records of the Department.
Proof of service of any notice or order in the manner specified by this section shall be made by the certificate or affidavit of any officer, employee, or agent of the District, naming the person on whom the notice or order was served and specifying the time, place, and manner of service.
The Chief of the Metropolitan Police Department or his or her agent shall take such action as may be necessary to serve any notice or order issued under the authority of the Act and the provisions of this chapter on the person affected by the notice or order.
D.C. Mun. Regs. tit. 18, r. 18-802