Montana Part-Year Resident Taxable Income Doesn't Make Sense to Me

[sampatg]

I have looked through the MT state tax return instructions, searched through the forums, and seen a lot of posts related to Montana using the federal taxable income as the base for calculating the Montana taxable income, but I am still confused. 

Last year I lived in Colorado until the fall of 2023, when I moved to Montana. I inputted all of the information related to this move into TurboTax. When doing the state return, it asked me to input my source income for the months I lived in Montana, so that it could calculate my part-year resident ratio. I did all of that, but when I got to the Montana Tax Return Summary, my Montana Taxable Income still reflected my federal income. It was the Montana adjusted income (total federal income minus restaurant tips I made in Colorado) minus standard deductions and personal exemptions. This amount was still well above the total income I made while living in Montana. 

Is anyone able to explain why this would be? Is this a bug/problem with TurboTax, or does the Montana Taxable Income shown on the Montana Tax Return Summary not reflect the actual taxed amount that comes from the source income and part-year resident ratio?

I saw some people mention the Credit for Income Tax Paid to Another State or Country Schedule. Should I be filling this section out and put my total Colorado income in there?

[sarareddy]

Montana Part-Year Resident Taxable Income Doesn’t Make Sense to Me either. Cheers! 

[AmyC]

Montana calculates a tax liability based on your full income for the year to start the calculation. Then, it prorates it based on your Montana percentage of income. See page 8 for the calculation.