D.C. Mun. Regs. tit. 3, r. 3-903
When a member of the Council resigns his or her office prior to the expiration of the term, the resignation shall be in writing and in duplicate.
The resigning member of the Council shall forward one (1) duplicate original of the resignation to the Mayor and one (1) duplicate original to the Chairperson of the D.C. Board of Elections.
Within five (5) working days of receipt of the duplicate resignation, the Board shall certify the seat vacant, effective as provided by the resignation, and issue the appropriate notification as provided in this chapter.
When a member of the Council dies while still serving his or her term of office, the Board shall, within five (5) working days of notice of the death of the member of the Council, certify the seat vacant and issue the appropriate notification as provided in this chapter.
When a vacancy in the office of Member of the Council is declared by court order, the Board shall, as soon as practicable after the court declaration, notify the Chairman of the Council of the vacancy by registered mail and provide any other notice as required in this chapter.
When a vacancy occurs in the office of Member of the Council as a result of a recall election, the Board shall, as soon as practicable after certification of the election results, certify the seat vacant and issue the appropriate notification as provided in this chapter.
D.C. Mun. Regs. tit. 3, r. 3-903