D.C. Code § 5-105.04

No person shall receive a permanent appointment who has not served the required probationary period, but the service during probation shall be deemed to be service in the uniformed force if succeeded by a permanent appointment, and as such shall be included and counted in determining eligibility for advancement, promotion, retirement, and pension in accordance with existing law. If at any time during the period of probation, the conduct or capacity of the probationer is determined by the Mayor of the District of Columbia, or his designated agent, to be unsatisfactory, the probationer shall be separated from the service after advance written notification of the reasons for and the effective date of the separation. The retention of the probationer in the service after satisfactory completion of the probationary period shall be equivalent to a permanent appointment therein.