I am having trouble not double paying taxes for my state returns. I have income in two states (ID resident, MT non-resident). When I file my state taxes, TurboTax asks for my federal AGI for both stat

[ColeenD3]

All income is taxable to your home state. Some non-resident states prorate the income. Some, like MT, report the entire income and then prorate. You will have to file a tax return and possibly pay if you are over the filing requirement for MT. You might be entitled to a credit for taxes paid to another state if some or all the income taxed by Idaho is also taxed by another state.

Nonresident/Part-Year Resident Ratio Schedule (MT)

If you are a nonresident or part-year resident, you have so far reported your income as if you were a resident. You also calculated your tax as a resident on the Tax Liability Schedule, line 2. You must use this Schedule to reduce your income tax to the portion related to your Montana source income.

This is from 2018, but it was the most complete information I could find. 

MT NR

[chrisbe2u]

I wrote this in the helper on the mobile app, which told me to include as many details as possible and then apparently cuts off the message afterwards without telling you there is a character limit. Neat, but contradictory and unhelpful, TT.

Here's the rest of the situation.

Turbotax asks for federal AGI for both state returns, which I supply.  For the ID return, it asks for income that has been double taxed (do I put in ALL my income from both states, because it is being taxed by both states, or just the stuff that ID shouldn't be taxing from MT?) 

For the MT return, Turbotax doesn't seem to actually do anything. It asks for my federal AGI, then my MT income, then subtracts. But when it comes time to actually claim the income, it doesn't use that difference. It just puts in my full AGI, including ID income. There doesn't seem to be any prorating, subtraction, or even acknowledgement that my taxable income for MT is being adjusted from the AGI for the final calculations, even though TT asks for the income to be separated on the MT state return step. For all real purposes, TT seems to be treating all my income as resident MT income even though it knows I am not a resident, thus making me pay full income tax on all my income to two different states.

Is TT just not showing some math or process?

[chrisbe2u]

Let me throw in another curveball. None of my ID income has been previously withheld (it's all fellowship processed as student financial aid, not W4 income). So technically, I have not paid any tax on it until the return filing.

[MarilynG1]

Report your Fellowship Income in the Education section, with any offsetting Education Expenses.

Click this link for info on entering Fellowship Income. 

Report all your income from all sources to your Resident State of Idaho.

Report only Montana income/taxes on your Non-Resident State Return to MT.  Prepare this return first. 

Click this link for more info on How to File a Non-Resident Return. 

Most states start with Federal AGI, then have different methods to apportion tax on income from that state.