MD doesn't get to tax that retirement distribution since you weren't living there when received. But, the part-year Maryland Form has a terrible way of having taxpayers allocate the proper amount of income that was earned/received during the period of nonresidence - they make you enter the entire income amount as one number. No separation of income types to help.
So, when TT/MD asks for you to enter the "Income received during period of nonresidence" (or whatever it says) you have to have that number already figured out and ready. That amount is subtracted out of total income as one of the amounts to arrive at Maryland adjusted gross income. So, for instance, figure out how much of total wages were earned while a PA resident; figure out how much of total interest income was earned while a PA resident; the 401(k) withdrawal is one of those $$; and so forth, and add it all up. That's the number to enter there.
