D.C. Mun. Regs. tit. 1, r. 1-2212
The NOI must be served on the violator, the business owner, or the owner's agent by means of certified mail, personal service or conspicuous posting.
An NOI served via U.S. mail must be sent to the respondent's last known home or business address.
If service is made by certified mail, the petitioner must provide a copy of the return receipt of certified mail to the Office of Administrative Hearings within fifteen calendar days after a case is filed.
If service is made by personal delivery, the petitioner may provide a certificate of service signed by the issuing agent.
If service is made by posting, the petitioner must provide an affidavit of posting, stating when the NOI was posted and the duration of the posting.
D.C. Mun. Regs. tit. 1, r. 1-2212