You can submit DC Form D-40B to get a refund of your withheld DC taxes. Here's a link: https://otr.cfo.dc.gov/sites/default/files/dc/sites/otr/publication/attachments/2016%20D-40B%201.06....
And, if you haven't done so already, you should submit DC Form D-4A to your employer. Here's a link to that: https://www.bea.gov/jobs/new_employees/docs/D-4A_Certificate_of_Nonresidence.pdf
The only published exceptions to the underpayment penalty in Maryland are:
1. The tax liability on gross income after deducting Maryland withholding is $500 or less; or
2. You have made four quarterly payments as required, each equal to or more than one-fourth of 110% of last year’s taxes.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
