Thanks to D. for sending. This question comes up fairly regularly. The Department of For-Hire Vehicles has previously told us:
“The Department of For-Hire Vehicles, which regulates taxicabs, limos, and ride-hailing companies in the District, allows residents of Maryland and Virginia to operate in the District. One requirement is to display a taxi vehicle tag issued by the District. In the past, some taxicabs had tags issued both by the District and their home jurisdiction. That is why you may occasionally see taxicabs with two tags.”