I am currently working in VA and have a apartment here. My wife is going to work in MD and will have a apartment there. I am confused about the tax file next year. If she keep the VA driver license, what is tax situation going to be? What if she exchange MD driver license? Can we still file jointly next year?
Thanks

If you are filing federal return as joint return, then you will file state returns as joint returns.

For MD, your wife is a part year resident or full year resident and will pay MD tax. You are a nonresident and do not have any MD income.

If your wife is part year resident of MD and is considered resident of VA, then she will also report her MD income on the VA tax return. She will also claim credit for the taxes paid to MD.
Read: Your U.S. Tax Return: Working or Living in Two or More states (http://taxipay.blogspot.com/2008/06/working-in-two-or-more-states.html)