D.C. Mun. Regs. tit. 18, r. 18-421
Whenever a motor vehicle for which current registration is required is being operated upon any public highway, or trailer for which current registration is required is being moved upon any public highway, and owner's identification tags are displayed on the motor vehicle or trailer, the registration card for the motor vehicle or trailer shall at all times be carried in the vehicle to which it refers or shall be carried by the person driving or in control of the vehicle, who shall display the registration card, upon demand, to a police officer or the Director.
The requirements of this section shall not apply when the card is used for the purpose of making application for renewal of registration or upon a transfer of registration of the vehicle.
D.C. Mun. Regs. tit. 18, r. 18-421