Yes. Your state of residence can tax you on all your earnings, regardless of where earned. Because of tax reciprocity, you do not have to file a DC return. But your DC earnings are fully taxable by PA.
If your employer mistakenly withheld DC taxes, submit DC Form D40-B to obtain a refund. You can find a link to that form on this web page: http://otr.cfo.dc.gov/node/424492
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
