I see a few answers on here pointing us to the www.mass.gov FAQ. I know the answer from their point of view, but I want to know how to do this in TurboTax.
A co-worker figured this out. When TurboTax asks if any other states show up in box 15 you have to choose "YES". This will then bring up the apportionment screen so that you can enter days working in and out of MA.
AND THEN Massachusetts REJECTS YOUR RETURN that you e Filed!!!!!
@Bobandroxie - Right, you may not be able to efile if you apportion. You will probably have to mail it in. This trick is just to get TurboTax to bring up the apportionment details, it will not show up on your return anywhere. It's a failure of TurboTax to not ask this question by default. According to the MA Dept. of Revenue, you are allowed to apportion, you just need the proof to back it up and a letter from your employer is proof enough according to the MA DoR.
If you are past the question for box 15 how do you correct Turbo Tax entry to allow the apportionment screen to allow update?
@raugust4122 - I used the online version and with that you are able to go back to any question at anytime by choosing from the menu tabs at the top. Or you can click the "Back" buttons at the bottom. If you are not using the online version I would think it has similar options but am not certain.