According to Montana Instructions for Form 2, “you must file a Montana Individual Income tax return if your federal gross income meets the threshold and you lived or earned income in Montana during the tax year."
What are Montana's filing thresholds?
if during the tax year you were a resident or part-year resident of Montana, or if you were a nonresident who received Montana source income; and you had a requirement to file a federal tax return, then you
must file a Montana income tax return. If you did not have a federal filing requirement, but have a
Montana addition or subtraction, you also must file a Montana income tax return
Can I use a different filing status than my Federal tax return?
Montana does not require you to claim the same filing status that you claimed on your federal return. You may choose a different filing status for your Montana return. However, starting with the 2024 tax year, Montana will require you to use the same filing status you used on your federal return.
What if I live in a reciprocal state?
Montana and North Dakota have a reciprocal agreement. If a Montana resident works or performs personal/professional services for an employer in North Dakota, the wages are treated as being earned in Montana and the Montana resident does not have to file a North Dakota income tax return reporting those wages.