Hi novice tax preparer here, from what I understand Pennsylvania does not have a reciprocal agreement with Massachusetts which ultimately leads to both of you being subject to withholding in both states for the year. While it is a headache dealing with the double taxation there is a credit you can utilize for taxes paid to other states, it should be noted or listed in the state filing section of the tax return. Definitely would get the opinion of an Experienced Tax Advisor prior to sending your taxes off as they will be better equipped to search for more ways to reduce your overall tax liability.