The decision of the Director shall include the following:
The Director shall serve upon the respondent, or his or her attorney of record, a copy of the written decision, either by personal service or certified mail, return receipt requested. If served by certified mail, it shall be deemed served on the date contained on the return receipt for acceptance or refusal, or the date of the unsuccessful attempt by the United States Postal Service to make delivery.
D.C. Mun. Regs. tit. 22, r. 22-B424