PA Resident Working in MD

Submit exemption Form MW 507 to your employer if you work in Maryland and are a resident of Pennsylvania and file a nonresident MD return for your MD refund.

You said " I am a PA resident working in MD. On my W2 this year, I had PA tax withheld."

That's what's supposed to happen.  You file only a PA return and include the MD income.  

If you meant to say they withheld MD, then see ee-ea's reply. 

@tlbuskirk 

Not sure I understand what you are saying.

1) You are a PA resident

2) Your W-2 shows PA taxes withheld.

Thar sounds exactly right.  

A) You pay PA taxes on your MD wages, and the PA withholding helps cover it.  Yes, you do file a PA resident tax return for ALL your income from everywhere.

B) You Do Not need to say you worked in another state (MD) since all those wages are considered to effectively be PA-Only income.   Thus, you do NOT file a MD nonresident tax return.