If you were never a resident of D.C. in 2021, file DC Form D-40B to obtain a refund of the incorrectly withheld D.C. taxes. Here's a link to the form:
https://otr.cfo.dc.gov/node/1576061
As a resident of MD in 2021, you will owe MD taxes on all your income. If you had no MD taxes withheld, you'll owe the entire amount.
If you live in MD but work in D.C., file DC Form D-4A with your employer to stop the D.C. withholding.
https://otr.cfo.dc.gov/sites/default/files/dc/sites/otr/publication/attachments/48019_2015_D-4A.pdf
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
