I assume you are currently a Virginia resident because you have a mortgage on a townhouse there.
If you lease an apartment in Washington DC and continue to maintain your Virginia residency, you will be a resident of both Washington DC and Virginia.
Statutory resident
DC considers an individual to be a “statutory resident” if they maintain a place of abode within the District for an aggregate of 183 days or more during the taxable year, whether or not they are domiciled in the District, i.e. consider the District to be their permanent residence.
See: What is the meaning of statutory residency?
Virginia residents who commute to DC normally do not pay to file or pay DC income tax due to a reciprocal agreement between the two states.
However, being a statutory resident means you will have to file a DC return and pay DC income tax. You will also have to file and pay VA tax. You can claim a credit on double-taxed income on the DC return.
Statutory nonresidents
The following are considered statutory nonresidents:
- Elected member of the US government who was not domiciled in DC;
- An employee on the personal staff of an elected member of the US Congress and you and the elected member were bona fide residents of the same state;
- Member of the US Executive Branch appointed by the President, subject to US Senate confirmation, whose tenure of office is at the pleasure of the President and you were not domiciled in DC during any part of 2020; or
- Justice of the US Supreme Court and were not domiciled in DC during any part of 2020.
