Residency Migration Reference
Moving from Idaho to Montana: Residency, Taxes, and What to Prove
Idaho's 5.30% top income tax rate becomes 5.65% in Montana. This move trades a lighter tax environment for a heavier one, so timing income around the transition year matters.
Residency Tests Side by Side
Idaho's statutory residency test uses a 270-day threshold. Montana does not use a simple day-count threshold; it applies a facts-and-circumstances test instead.
| Factor | Idaho | Montana |
|---|---|---|
| Statutory Residency Test | Idaho Code §63-3013 defines a resident as an individual either domiciled in Idaho for the entire taxable year, or someone who maintains a place of abode in Idaho for the entire taxable year and spends in the aggregate more than 270 days of the taxable year in Idaho, a materially higher threshold than the 183-day test most states use. Presence within the state for any part of a calendar day counts as a full day toward that 270-day total. | Under ARM 42.15.109, implementing Mont. Code Ann. §15-30-2101, an individual is a Montana resident for income tax purposes if domiciled in Montana or if the individual maintains a permanent place of abode in Montana. Unlike most states, Montana's rule does not pair the permanent-place-of-abode prong with a codified day-count threshold; residency for the abode prong is instead determined, per the regulation's own language, 'in light of all facts and circumstances.' |
| Domicile Test | Idaho defines domicile administratively (IDAPA 35.01.01.030 and the Tax Commission's public guidance) as the place that is the center of an individual's personal and business life, the permanent home a person intends to return to whenever absent. An individual can have multiple residences but only one domicile at a time, and once established, domicile persists until it is affirmatively abandoned, a new one is acquired, and the person is actually living in the new domicile. Evidence weighed includes where the family lives, comparison of homes in different states, where business activity occurs, how time is actually spent during the year, where sentimentally important belongings are kept, and whether the person has given up an Idaho driver's license or the Idaho homeowner's exemption. | 'Domiciled' is defined by ARM 42.2.304 as having a residence in Montana as determined under Mont. Code Ann. §1-1-215, the state's general residence statute. That statute treats residence as the place a person returns to in seasons of repose when not called elsewhere for labor or a special or temporary purpose, holds that a person can have only one residence, that a residence cannot be lost until another is gained, and, notably, that if a person claims a Montana residence for any purpose, that location becomes the person's residence for all purposes absent a specific statutory exception. A change of residence requires the union of act and intent, not one alone. |
| Day Count Threshold | 270 days | No fixed threshold |
| Any Part of a Day Rule | Yes. Idaho Code §63-3013(1)(b) explicitly states that presence within the state for any part of a calendar day counts as a full day toward the 270-day aggregate threshold, the strict any-part-of-a-day standard. | Montana's regulations do not publish a specific any-part-of-a-day counting convention, because the permanent-place-of-abode prong of the residency test has no attached day-count threshold at all; the Department instead applies a facts-and-circumstances standard to the abode question. |
| Presumptions | None published as a separate presumption distinct from the domicile-plus-270-day statutory test; Idaho instead runs its 445-day absence safe harbor (below) as the primary mechanism for domiciled Idahoans to be treated as nonresidents. | None published as a distinct numeric presumption. The general residence statute's 'claim a residence for any purpose, and it's your residence for all purposes' rule functions as Montana's closest analog to a presumption: registering to vote, obtaining a resident hunting or fishing license, or otherwise claiming Montana residency for an unrelated purpose can be used as evidence of Montana domicile for tax purposes. |
| Safe Harbors | 445-day absence exception | None published |
Leaving Idaho
Idaho is not commonly named among the states practitioners flag as aggressive on residency (California, New York, New Jersey, Connecticut, Maryland, Minnesota), but its 445-day absence exception has built-in disqualifiers that create real exposure for people who assume a long posting abroad or out of state automatically converts them to nonresident status. The exception is unavailable if a spouse or minor children keep living in an Idaho home more than 60 days a year, if the person claims Idaho as their federal tax home for away-from-home expense deductions, or in specific federal-employment situations, which means a family that stays behind in Idaho while one spouse works elsewhere does not get the safe harbor even after a long absence.
Trailing Income
Idaho-source income, including income from Idaho real property, an Idaho business, or work physically performed in Idaho, remains taxable to nonresidents after departure. Idaho has no convenience-of-employer rule reaching remote workers who have genuinely relocated, and interstate rail and motor carrier employees with regularly assigned duties in more than one state are, by federal law, taxable only in their state of residence rather than every state they pass through.
Part-Year Filing
Form 43, the Idaho Part-Year Resident & Nonresident Income Tax Return, used to report income while an Idaho resident plus any Idaho-source income earned before arriving or after leaving; spouses with different residency status who file a joint federal return must also file a joint Idaho Form 43.
Enforcement Methods
Common Exit Mistakes
Establishing Montana Residency
| Action | Agency | Deadline |
|---|---|---|
| Get a Montana driver's license | Montana Motor Vehicle Division | within 60 days of establishing residency |
| Title and register vehicles in Montana | Montana Motor Vehicle Division / county treasurer | within 60 days of establishing residency |
| Register to vote | Montana Secretary of State / county election office | regular registration closes 30 days before an election; late registration continues through Election Day (subject to a noon-to-5pm blackout the day before) |
Declaration of Domicile
Montana has no formal declaration-of-domicile filing comparable to Florida's for tax purposes. What Montana does have is a homestead declaration, a separate, unrelated legal mechanism (see Homestead below) that protects home equity from creditors, not a domicile filing, though a recorded homestead declaration is one more piece of paper trail pointing to where a person has claimed Montana as home.
Homestead
Montana's homestead exemption (Mont. Code Ann. §70-32-104) is not automatic: a person must execute, notarize, and record a written declaration of homestead with the county clerk and recorder (§70-32-105) to claim it. It protects home equity from most creditors up to a dollar cap that started at $350,000 in 2021 and adjusts upward roughly 4% a year. Because the declaration is a deliberate, dated, recorded filing rather than something automatic, it functions as unusually strong documentary evidence of when a person claimed a Montana home, useful for establishing residency, but also a loose end that should be released if the property stops being the primary home.
Voter Registration
Regular registration closes 30 days before an election; Montana also allows late registration in person through Election Day itself, though a court fight over Senate Bill 490 has centered on a proposed blackout period the day before Election Day, so voters moving close to an election should confirm current rules with their county election office. https://votemt.gov/voter-registration/
Vehicle Registration Deadline
60 days
New Resident Tax Traps
Montana taxes worldwide income from the date Montana domicile begins, requiring Montana Form 2's part-year apportionment for the year of the move. Because Montana's general residence statute treats a claim of Montana residency for any purpose as a claim for all purposes, a new arrival who registers to vote or gets a resident hunting license before formally establishing the rest of their domicile picture may find the state (or their old home state) pointing to that early claim as the actual date domicile began.
What Changes on Tax
Idaho Top Rate
5.30%
Montana Top Rate
5.65%
Moving from Idaho to Montana raises the top marginal income tax rate from about 5.3% to about 5.65%, an increase of roughly 0.35 percentage points.
Withholding Reciprocity
Idaho and Montana do not have a wage-withholding reciprocity agreement with each other, so this move follows ordinary source-state and resident-state filing rules rather than a reciprocity exception.
Community Property Transition
Idaho is a community property state and Montana uses common law marital property rules. Property already characterized as community property generally keeps that character after the move, subject to the destination state's quasi-community-property treatment, while future acquisitions follow Montana's common law rules.
Beyond Income Tax
Idaho
Capital gains: Taxed as ordinary income at the flat rate, but Idaho allows a deduction of 60% of the net capital gain from the sale of qualifying Idaho property under Idaho Code §63-3022H. Qualifying property generally means Idaho real property held at least 12 months (18 months if sold before January 1, 2005), or certain business assets, cattle, and horses held for the required period; the deduction is claimed on Form CG and does not apply to gains on out-of-state property or most financial assets.
Estate or inheritance tax: None. Idaho has no estate tax and no inheritance tax.
Property tax: Effective rate is roughly 0.50% of value. Idaho's Homeowner's Exemption exempts 50% of a primary residence's assessed value up to a $125,000 cap (Idaho Code §63-602G), but unlike an automatic homestead protection this requires an affirmative application with the county assessor and lasts only until ownership changes or the home stops being the owner's primary residence, making it an easy domicile cross-check point.
Sales tax: 6.00% state rate, with a low average combined state-and-local rate of about 6.03%, since Idaho has very limited local-option sales taxes (mostly a handful of resort cities).
Montana
Capital gains: Long-term capital gains are carved out of ordinary taxable income and taxed on their own, lower two-bracket schedule: 3.0% and 4.1% for 2026 and 2027, with the bracket break points tracking the ordinary-income bracket structure. Short-term gains are taxed as ordinary income at the regular 4.7%/5.65% rates.
Estate or inheritance tax: None. Montana has no estate tax and no inheritance tax.
Property tax: Effective rate is roughly 0.61% of value. Montana's homestead exemption is not a property-tax break at all but a creditor-protection filing (see Establish); property tax relief instead comes through separate, income-limited programs like the Property Tax Assistance Program and Elderly Homeowner/Renter Credit.
Sales tax: Montana has no general state or local sales tax, one of only five states without one. This is also why out-of-state buyers sometimes register high-value vehicles and RVs through Montana LLCs to avoid their home state's sales tax, a business-registration workaround that has no bearing on personal tax domicile.
Who This Move Applies To
Travel Nurses
In Idaho
Boise's hospital systems and Idaho's rural-hospital travel contracts make the state a modest but real travel-nurse market. A nurse genuinely domiciled in Idaho who takes Idaho contracts is simply taxed as a resident. A nurse claiming an Idaho tax home while working elsewhere needs a real, regularly used, duplicated-expense Idaho residence; claiming Idaho as a federal away-from-home tax home while also trying to use the 445-day absence exception for Idaho state tax purposes is explicitly disqualifying under Idaho's own rule, so the two claims cannot be made consistently.
In Montana
Billings, Missoula, and Montana's regional hospital systems generate real but modest travel-nurse demand given the state's population. A nurse genuinely domiciled in Montana who takes Montana contracts is taxed as an ordinary resident. A nurse claiming a Montana tax home while working elsewhere needs a real, regularly used, duplicated-expense Montana residence, since Montana's facts-and-circumstances domicile standard applies the same evidentiary weight to a claimed tax home as it does to any other domicile dispute.
Professional Athletes
In Idaho
Idaho has no major professional sports franchise in the four big US leagues, so jock-tax exposure runs almost entirely one direction: Idaho-domiciled or Idaho-resident athletes are taxed on income earned while playing in other states under those states' own apportionment rules, and nonresident athletes visiting Idaho for occasional events owe Idaho tax on Idaho-source duty days under the state's standard nonresident income sourcing.
In Montana
Montana has no major professional franchise in the four big US leagues, so jock-tax exposure runs primarily one direction: Montana-domiciled athletes playing professionally elsewhere are taxed by those other states under their own apportionment rules, while nonresident athletes competing in occasional Montana events (college sports revenue aside) owe Montana tax on Montana-source income under standard nonresident sourcing.
Snowbirds, Long Visitors, and RVers
In Idaho
Idaho's 270-day statutory threshold is unusually generous compared to the 183-day standard most states use, but it comes paired with the strict any-part-of-a-day counting rule, so a snowbird or long-term visitor who owns or leases an Idaho home needs to track every day with any Idaho presence, not just overnight stays, against that 270-day ceiling. Idaho's own seasonal-worker example (a couple splitting time between an Alaska fishing operation and an Idaho off-season home) shows the state applies the ordinary domicile-or-270-day test to seasonal residents just as it would to anyone else, with no special seasonal carve-out.
In Montana
Because Montana's permanent-place-of-abode test has no codified day-count threshold, a long-term visitor or second-home owner in a resort area like Whitefish, Big Sky, or the Flathead Valley cannot rely on staying under a specific number of days the way they could in a state with a 183-day rule; the Department instead weighs the full facts and circumstances of how the home is used and how much time is actually spent there. Montana's own domiciliaries who winter in Arizona or elsewhere remain presumed Montana residents under the 'residence cannot be lost until another is gained' rule unless they affirmatively establish a new domicile.
Remote Workers
In Idaho
Idaho has no convenience-of-employer rule: a nonresident performing all work physically outside Idaho for an Idaho-based employer is not Idaho-taxed on those wages. Idaho, particularly the Boise metro area, has drawn a steady stream of remote workers relocating from higher-cost West Coast states since 2020; because Idaho and Washington are both community property states, a remote-working couple split between the two needs to account for the community-property income-sharing rule on their Idaho return, not just source-based sourcing.
In Montana
Montana has no convenience-of-employer rule: a nonresident performing all work physically outside Montana for a Montana-based employer is not Montana-taxed on those wages. Montana, particularly Bozeman, Missoula, and the Flathead Valley around Whitefish and Kalispell, has drawn a wave of remote workers relocating from higher-cost states since 2020, and the lack of a sales tax is a frequently cited draw alongside the income tax simplification.
Military
In Idaho
Idaho follows the federal Servicemembers Civil Relief Act and Military Spouses Residency Relief Act, and Idaho's own guidance walks through the distinction between military home of record and state of legal residence/domicile: a service member stationed in Idaho under orders (for example, at Mountain Home Air Force Base) is taxed based on domicile, not the posting, active-duty military pay is not Idaho-taxed for nonresident service members, and a nonmilitary spouse can independently be a resident, part-year resident, or nonresident depending on their own domicile and MSRRA elections.
In Montana
Montana follows the federal Servicemembers Civil Relief Act and Military Spouses Residency Relief Act. A service member stationed in Montana under orders (Malmstrom Air Force Base near Great Falls is the state's major installation) does not become Montana-domiciled from the posting alone. Montana's 2024 tax simplification added a subtraction for certain resident working military retirees and military survivor-benefit recipients, on top of the general federal SCRA/MSRRA protections.
Airline Crew
In Idaho
Boise Airport is not a major airline crew base, so Idaho's most relevant federal transportation carve-out runs to interstate rail and motor carrier employees rather than airline crew specifically: Idaho's guidance confirms that employees of interstate rail or motor carriers with regularly assigned duties in more than one state are, under federal law, taxable only in their state of residence, with the Idaho-earned portion of a nonresident's income remaining Idaho-taxable.
In Montana
Montana's airports (Bozeman Yellowstone International being the busiest) are not major airline crew bases, so the more relevant federal carve-out for Montana residents working in transportation is the interstate rail and motor carrier employee rule: federal law limits taxation of such employees with regularly assigned duties in more than one state to their state of residence.
Tools for This Move
Idaho to Montana FAQ
Does Idaho use the 183-day rule?+
No. Idaho's statutory residency threshold is 270 days, not 183, and any part of a calendar day with Idaho presence counts as a full day toward that total under Idaho Code §63-3013(1)(b). You're a statutory resident if you maintain a place of abode in Idaho for the entire year and hit that 270-day aggregate, independent of domicile.
Does Montana use the 183-day rule?+
No. Montana's residency test is domicile or maintaining a permanent place of abode in the state, but unlike most states, the permanent-place-of-abode prong has no codified day-count number at all. The Department looks at all the facts and circumstances of how the home is used rather than counting to a specific threshold like 183 days.
I'm domiciled in Idaho but working out of state for years. Am I still an Idaho resident?+
Not necessarily, if you qualify for Idaho's 445-day absence exception: being out of Idaho for at least 445 days within a 15-month period lets a domiciled Idahoan be treated as a nonresident. But the exception doesn't apply if your spouse or minor children keep living in your Idaho home more than 60 days a year, or if you claim Idaho as your federal tax home for away-from-home expenses.
If I get a Montana hunting license or in-state tuition after I've moved away, does that make me a Montana resident again?+
It can be used against you. Montana's general residence statute says that if you claim Montana residence for any purpose, that becomes your residence for all purposes unless a specific statutory exception applies. Claiming a resident hunting license or resident tuition after claiming to have left is exactly the kind of inconsistent claim the Department, or your new home state, could point to.
How many months can I spend in Idaho as a snowbird before I owe Idaho income tax?+
Up to 270 days in the aggregate during the year, since Idaho's statutory residency test kicks in above that threshold for anyone maintaining an Idaho place of abode. But Idaho counts any part of a day as a full day, so short visits add up faster than in states with a majority-of-day rule.
Does registering my RV or truck through a Montana LLC make me a Montana resident?+
No. Registering a vehicle through a Montana-formed LLC is a business registration, not a personal residency claim, and by itself has no bearing on your individual tax domicile. It doesn't make you a Montana resident, and it doesn't get you out of your actual home state's residency test either.
What form do I file if I only lived in Idaho part of the year?+
Form 43, the Idaho Part-Year Resident & Nonresident Income Tax Return. If you and your spouse have different residency statuses and file a joint federal return, you must also file a joint Idaho Form 43, with each spouse's status listed separately.
What form do I file if I only lived in Montana part of the year?+
Montana Form 2, the Individual Income Tax Return, filed with the part-year/nonresident schedule, which apportions your income between the period you were a Montana resident and the period you were not.
Does Idaho tax Social Security?+
No. Idaho fully exempts Social Security benefits from state income tax. Other retirement income like pensions, 401(k), and IRA withdrawals is generally taxed at the flat 5.30% rate, though a separate Retirement Benefits Deduction covers qualifying public-system pensions for taxpayers 65 and older or 62 and disabled.
Does Montana tax Social Security?+
Yes, but only to the extent it's included in your federal taxable income, following a 2024 simplification that ended Montana's older, separate and more restrictive Social Security worksheet. Taxpayers 65 and older also get a flat $5,500 subtraction from federal taxable income ($11,000 for a joint return where both spouses are 65+).
Does Idaho have a capital gains tax break?+
Idaho taxes capital gains as ordinary income but allows a 60% deduction on net gains from qualifying Idaho property, generally real property held at least 12 months, claimed on Form CG. The deduction is specific to Idaho property; gains on out-of-state real estate or most stocks and financial assets don't qualify.
Does Montana tax capital gains differently from ordinary income?+
Yes. Long-term capital gains are pulled out of ordinary taxable income and taxed on their own lower two-bracket schedule, 3.0% and 4.1% for tax years 2026 and 2027, well below the 4.7%/5.65% rates on ordinary income. Short-term gains are taxed as ordinary income at the regular rates.
Considering the reverse move?
Montana to Idaho
Moving the other direction is a different fact pattern, not a mirror image: exit risk and establishment mechanics both flip.
View the Montana to Idaho guideAlso Consider, Leaving Idaho
Idaho to Montana Reading
Reviewed Against 26 Primary Sources
ResidencyIQ organizes public residency research into a reviewable reference. It does not provide legal or tax advice. Consult a qualified professional before making a residency decision.
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