D.C. Mun. Regs. tit. 25-E, § 803
803.1 Proof of proper service may be made by certificate of service signed by the person making service or by admission of a return receipt, certificate of mailing, or a written acknowledgment signed by the licensee or person operating a barber, cosmetology, or personal grooming facility without a license or an authorized agent.
SOURCE: Final Rulemaking published at 68 DCR 013026 (December 10, 2021).