You are a resident of Montana for individual income tax purposes if you live in Montana or if you maintain a permanent home in Montana. A permanent home in Montana means a dwelling place you habitually use as your home, whether or not you own it and whether or not you may someday leave. You do not lose your Montana residency if you leave the state temporarily with the intention of returning. Your Montana residency is lost when you move outside of Montana with no intention of returning. Unless there is a specific exception under Montana law, if you establish Montana residency for any other purpose, you are considered a Montana resident for income tax purposes.
You are a nonresident of Montana if you were not a resident during any part of the tax year.
You are a part-year resident of Montana if you moved to or from Montana during the tax year with the intention of establishing a permanent residence in your new state. A nonresident or part-year resident who is required to file a Montana tax return needs to use Form 2.