Residency Migration Reference
Moving from Kentucky to Idaho: Residency, Taxes, and What to Prove
Kentucky's 3.5% (flat rate, tax year 2026) top income tax rate becomes 5.30% in Idaho. This move trades a lighter tax environment for a heavier one, so timing income around the transition year matters.
Residency Tests Side by Side
Kentucky uses a 183-day statutory residency threshold, while Idaho uses 270 days. Track both thresholds separately during a transition year rather than assuming they line up.
| Factor | Kentucky | Idaho |
|---|---|---|
| Statutory Residency Test | KRS 141.010 defines a resident as an individual domiciled in Kentucky, or an individual not domiciled in Kentucky who maintains a place of abode in the state and spends, in the aggregate, more than 183 days of the taxable year in Kentucky. Both prongs, an abode plus more than 183 aggregate days, are required for someone without Kentucky domicile to be taxed as a statutory resident. | 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. |
| Domicile Test | 103 KAR 17:010 defines domicile simply as the place an individual has established permanent residency, and states that a domicile once obtained continues until a new one is acquired: it is not changed by removal for a definite period or for incidental purposes. A change of domicile requires three elements together: intent to change, actual removal, and establishment of a new abode. The regulation does not publish a weighted multi-factor list the way New York's guidelines do; the three-element test is applied to the facts case by case. | 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. |
| Day Count Threshold | 183 days | 270 days |
| Any Part of a Day Rule | Kentucky's regulation does not define whether a partial day counts, unlike New York's explicit any-part-of-a-day rule. The statute counts days in the aggregate across the year, so practitioners generally treat any day with in-state presence as counting toward the 183-day threshold absent published guidance to the contrary. | 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. |
| Presumptions | 103 KAR 17:010, Section 2 creates a boomerang presumption: if someone who moved out of Kentucky returns to Kentucky within six months of the move, the state treats the departure as not intended to be permanent, and the individual is considered a resident (or part-year resident for the period the abode was elsewhere) for that time. Section 4 separately presumes a Kentucky domiciliary who moves abroad and files as a federal nonresident citizen is still a Kentucky resident, unless they present sufficient evidence the Kentucky domicile was abandoned. | 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. |
| Safe Harbors | None published | 445-day absence exception |
Leaving Kentucky
Kentucky is not commonly named among the aggressive exit-audit states the way New York, California, or Connecticut are, and no widely published landmark residency case defines Kentucky's enforcement posture the way Gaied or Bragg do for other states. The clearest, best-documented exit trap is the six-month boomerang rule in 103 KAR 17:010: anyone who moves out of Kentucky and returns within six months is automatically treated as never having genuinely left. Federal employees and career military domiciled in Kentucky before leaving also face a higher bar, needing conclusive evidence of domicile abandonment under Sections 5 and 6 of the regulation.
Trailing Income
Kentucky does not have a published convenience-of-the-employer rule for remote workers. Kentucky-source income, including wages for work actually performed in Kentucky, business income sourced to Kentucky activity, and gains from Kentucky property, remains taxable to a nonresident after departure under ordinary sourcing principles reflected on Form 740-NP.
Part-Year Filing
Form 740-NP, the Kentucky Individual Income Tax Return for Nonresidents or Part-Year Residents, is used both for part-year residents who moved into or out of Kentucky during the year and for full-year nonresidents with Kentucky-source income. Residents of the reciprocal states (Illinois, Indiana, Michigan, Ohio, Virginia, West Virginia, Wisconsin) whose only Kentucky income is wages can instead use the simpler Form 740-NP-R to claim a full refund of any Kentucky withholding.
Enforcement Methods
Common Exit Mistakes
Establishing Idaho Residency
| Action | Agency | Deadline |
|---|---|---|
| Get an Idaho driver's license | Idaho Transportation Department | within 90 days of becoming an Idaho resident |
| Title and register vehicles in Idaho | Idaho Transportation Department / county assessor's motor vehicle office | within 90 days of moving to Idaho |
| Register to vote | Idaho Secretary of State / county clerk | 11 days before an election for mail or online registration; same-day registration is available at early voting locations and on Election Day with proof of residency |
Declaration of Domicile
Idaho has no formal declaration-of-domicile filing comparable to Florida's. The Tax Commission's own guidance points to concrete, checkable evidence instead: where your family lives, where you do business, how you actually spend your time during the year, where sentimentally important belongings are kept, and whether you've obtained an Idaho driver's license or filed for the Idaho Homeowner's Exemption.
Homestead
Idaho's Homeowner's Exemption (Idaho Code §63-602G) exempts 50% of a primary residence's assessed value, capped at $125,000, from property tax, but requires an affirmative application with the county assessor rather than applying automatically. It lasts only until ownership changes or the home stops being used as the owner's primary residence, so a person who moves out but forgets to cancel the exemption leaves an easy paper trail contradicting a claimed departure.
Voter Registration
Mail and online registration must be received 11 days before an election; Idaho also permits same-day registration in person at early voting locations and on Election Day with proof of residency. https://voteidaho.gov/voter-registration/
Vehicle Registration Deadline
90 days
New Resident Tax Traps
Idaho taxes worldwide income from the date Idaho domicile begins, requiring the Form 43 part-year apportionment for the year of the move. Because Idaho and Washington are both community property states, a couple where one spouse lives and works in Idaho and the other in Washington must generally report one-half of all community income, including the out-of-state spouse's earnings, on the Idaho return, a wrinkle that surprises newly arrived couples who assume only Idaho-source income is reportable.
What Changes on Tax
Kentucky Top Rate
3.5% (flat rate, tax year 2026)
Idaho Top Rate
5.30%
Moving from Kentucky to Idaho raises the top marginal income tax rate from about 3.5% to about 5.3%, an increase of roughly 1.8 percentage points.
Withholding Reciprocity
Kentucky and Idaho 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
Kentucky uses common law marital property rules and Idaho is a community property state. Property acquired during marriage after the move may be characterized differently going forward, which matters for estate planning and for basis step-up on a spouse's death.
Beyond Income Tax
Kentucky
Capital gains: Kentucky has no separate capital gains rate. Gains are included in federal adjusted gross income, which flows through to the Kentucky return and is taxed at the same flat rate as ordinary income.
Estate or inheritance tax: Kentucky has no estate tax but is one of a small number of states with an inheritance tax, administered under KRS Chapter 140. Class A beneficiaries (spouse, children, parents, grandchildren) and, as of a 2026 law change, Class B beneficiaries (siblings, nieces, nephews, aunts, uncles) are exempt. Class C beneficiaries (more distant relatives, friends, unrelated entities) get only a $500 exemption before rates of 6% to 16% apply. The return is due within 18 months of death.
Property tax: Average effective property tax rate is about 0.74%, below the national average. The homestead exemption for owners 65 or older or totally disabled deducts $49,100 from assessed value for the 2025-2026 assessment cycle, with no income test, and the exempted amount adjusts every two years for inflation.
Sales tax: State sales tax rate is 6%, and Kentucky does not permit local add-on sales taxes, so 6% is also the effective combined rate statewide.
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).
Who This Move Applies To
Travel Nurses
In Kentucky
Kentucky applies the same domicile and 183-day statutory tests to travel nurses as to anyone else; there is no separate published carve-out. A nurse who is not domiciled in Kentucky but keeps a Kentucky apartment and accumulates more than 183 aggregate days in the state during assignments can be treated as a statutory resident taxed on worldwide income. The more common national pattern, a nurse claiming a no-tax-state tax home while actually living in a rental near the assignment, applies to Kentucky assignments the same way it does elsewhere.
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.
Professional Athletes
In Kentucky
Kentucky has no major-league NFL, NBA, MLB, or NHL franchise, so it lacks the visible 'jock tax' infrastructure seen in states with home franchises. Kentucky still applies its standard nonresident sourcing rules on Form 740-NP to any income a nonresident athlete, driver, or entertainer earns for events performed in Kentucky, such as competing at Churchill Downs or Kentucky Speedway, but there is no published Kentucky-specific duty-days regulation the way several other states have adopted.
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.
Snowbirds, Long Visitors, and RVers
In Kentucky
A snowbird who keeps a Kentucky home while wintering elsewhere needs to watch the 183-day aggregate threshold along with the abode requirement; unlike states with an any-part-of-a-day rule, Kentucky's statute counts aggregate days across the year rather than penalizing brief in-and-out trips as harshly. The bigger trap for someone trying to leave Kentucky altogether is the six-month boomerang rule: moving away and returning within six months is treated under 103 KAR 17:010 as proof the move was never intended to be permanent.
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.
Remote Workers
In Kentucky
Kentucky has no published convenience-of-the-employer rule. A nonresident who works remotely for a Kentucky employer while physically located and domiciled outside Kentucky is generally not taxed by Kentucky on that income, since Kentucky sources wages based on where the work is actually performed rather than the employer's location.
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.
Military
In Kentucky
Under 103 KAR 17:010 Section 6, which incorporates the federal Soldiers' and Sailors' Civil Relief Act (the predecessor to today's SCRA), a servicemember retains the domicile held when they entered the service. A Kentucky domiciliary who enters the military stays liable for Kentucky income tax on all income regardless of where they are stationed unless they affirmatively change domicile and submit conclusive evidence the Kentucky domicile has been abandoned and a new one established elsewhere.
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.
Airline Crew
In Kentucky
Federal law (49 U.S.C. §40116) limits states to taxing an air carrier employee's pay only in the employee's state of residence and any state where more than 50% of pay is earned, which protects flight crew who work through a Kentucky hub, such as UPS's Worldport operations in Louisville, from Kentucky taxing their full income solely because Kentucky is their duty station if they are domiciled elsewhere.
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.
Tools for This Move
Kentucky to Idaho FAQ
How many days can I spend in Kentucky before I become a resident for tax purposes?+
If you're not domiciled in Kentucky, you become a statutory resident only if you both maintain a place of abode in Kentucky and spend more than 183 aggregate days in the state during the tax year, under KRS 141.010. Both conditions have to be true together: days alone, without an abode, don't trigger statutory residency, and an abode alone, without exceeding 183 days, doesn't either.
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.
I moved out of Kentucky but had to move back a few months later. Does that reset my residency clock?+
No, and this is a Kentucky-specific trap. Under 103 KAR 17:010, Section 2, if you move out of Kentucky and return within six months, the state treats the original move as never having been intended to be permanent, and you're considered a resident, or part-year resident, for the entire period your abode was elsewhere. There's no exception listed for a job that fell through or a family emergency; the six-month rule applies regardless of the reason for returning.
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.
What does it actually take to change my domicile away from Kentucky?+
103 KAR 17:010 requires three things together: intent to change your domicile, actual physical removal from Kentucky, and establishment of a new abode elsewhere. A domicile once established continues until all three are met; simply leaving for a defined period, like a work assignment with a planned end date, or for an incidental purpose doesn't change it. Kentucky's regulation is notably shorter and less factor-heavy than states like New York, but the three-part test is still a real bar to clear.
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.
I'm in the military and my home of record is Kentucky, but I'm stationed elsewhere. Do I still owe Kentucky tax?+
Yes, generally. Under 103 KAR 17:010, Section 6, which applies the federal servicemembers' relief protections, you retain the domicile you had when you entered the service. If that domicile was Kentucky, you remain liable for Kentucky income tax on all your income regardless of where you're stationed, unless you affirmatively change domicile and can show conclusive evidence the Kentucky domicile has been abandoned and a new one established elsewhere.
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.
I work in Ohio but live in Kentucky (or vice versa). Do I have to pay tax to both states?+
Generally no, on wages. Kentucky has reciprocal agreements with Illinois, Indiana, Michigan, Ohio, Virginia, West Virginia, and Wisconsin, so wages and salaries earned in one of those states by a Kentucky resident are exempt from that state's income tax, and the reverse holds for residents of those states working in Kentucky. The Virginia agreement is narrower: it only applies to taxpayers who commute daily to work in the nonresident state. You need to file the right exemption certificate with your employer, such as Kentucky's Form K-4, to actually stop withholding.
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.
I moved abroad and file my federal return as a nonresident citizen. Am I still a Kentucky resident for state tax?+
Kentucky presumes yes, if Kentucky was your domicile immediately before you moved to the foreign country. Section 4 of 103 KAR 17:010 creates a presumption of continued Kentucky residency for nonresident citizens in this situation. You can overcome it, but you need to present sufficient evidence that you genuinely abandoned Kentucky domicile, not just that you now live and file federally as if abroad.
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.
Considering the reverse move?
Idaho to Kentucky
Moving the other direction is a different fact pattern, not a mirror image: exit risk and establishment mechanics both flip.
View the Idaho to Kentucky guideAlso Consider, Leaving Kentucky
Kentucky to Idaho Reading
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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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