D.C. Code § 40-202
No such lien shall be effective, however, unless a written notice containing the name and address of the injured person, the date of the accident, the name and location of the hospital, and the name of the person or persons, firm or firms, corporation or corporations alleged to be liable to the injured party for the injuries received, shall be filed in the Office of the Recorder of Deeds of the District of Columbia in a docket provided for such liens, prior to the payment of any moneys to such injured person, his attorneys, or legal representatives as compensation for such injuries; nor unless the hospital shall also mail, postage prepaid, a copy of such notice with a statement of the date of filing thereof to the person or persons, firm or firms, corporation or corporations alleged to be liable to the injured party for the injuries sustained prior to the payment of any moneys to such injured person, his attorneys, or legal representatives as compensation for such injuries. Such hospital shall mail a copy of such notice to any insurance carrier which has insured such person, firm, or corporation against such liability, where the name of such insurance carrier is ascertained.
D.C. Code § 40-202