To file a prior year tax return, use the link below to purchase the software.
Indicate under the Personal Information section that you earned income in another state. When completing your state tax returns, complete your current state return before the prior year return. See link below for instructions.
I found the way around the other suggestions which say to record your first state as the non-resident state first, then record your actual resident state. This is written for the 2017 version of TT and will be helpful if you have a W-2 from a BORDER STATE.
1) Go to Personal Info in your tax return. Make sure that in "Your Personal Info Summary", at the bottom, "Other State Income" contains the other state. I l ive in VA and had tax withheld from MD. The next pg "Did you make money in any other states?" says that for my situation "you don't need to enter [state x state y state z etc] if you ONLY earned W-2 income from an employer. They have an agrmt with VA not to charge you income tax." The states listed are YOUR BORDER STATES. This statement causes you to think you are done and to click NO, but you are not done (if this situation applies to you). Click YES I made money in states other than xx [your resident state]. Then click the state(s) below. Saying YES allows you to n fill out your 2 (or more) states' returns correctly. This is very important since in my case, I claim BORDER state and I get all of my withholding back. If you cannot claim BORDER state then you don't get 100% of the tax back.
These instructions are primarily to help you get 100% back if applicable for you. TT will walk you through this, you just need to know these tips.
2) Now when you go to your state return, you'll get a screen to buy a 2nd state. For me, I'm not doing that bc it's easy to follow the instructions on the MD site and fill out the form and send it to them on paper. So, I click continue bc TT makes you, then I cancel out of buying the other state. Now I have MD and VA showing up on my TT state screen. Now I edit my resident state, VA. It asks me if I am claiming BORDER STATE CALCULATION and since that is correct for my situation, I click YES. Enter your info as requested. Your filing status should be same as your Federal return. Voila! You should see a 100% refund.
Originally I did this a bit backward (or more directly, depending on how you think) and I went to Forms and somehow got the VA OSC schedule added to my return package (OSC=VA's version of the "credit for taxes pd to another state" form). I think it was there in the list of forms even though I never saw it created via the TT step-by-step. But when I entered my MD info there in an attempt to see if I could circumvent the other advice about deleting VA and doing MD first, the VA form OSC would not let me check the BORDER STATE box, so I wasn't getting a full refund. That is when I did the steps 1 & 2 above and I found that TT would let you choose BORDER STATE via the step-by-step.
Hope this helps! I surely didn't want to undo all my VA work and have to start over.