Residency Migration Reference
Moving from South Carolina to Idaho: Residency, Taxes, and What to Prove
The top income tax rate drops from 6% in South Carolina to 5.30% in Idaho. Establishing Idaho residency correctly is what protects that benefit.
Residency Tests Side by Side
South Carolina does not use a simple day-count threshold; it applies a facts-and-circumstances test instead. Idaho's statutory residency test uses a 270-day threshold.
| Factor | South Carolina | Idaho |
|---|---|---|
| Statutory Residency Test | South Carolina has no day-count statutory residency test. The Department of Revenue's own guidance states plainly: 'Unlike some states that tax a person as a resident who lives in the state for a specific period of time, such as 183 days, South Carolina does not have a minimum time that must be spent in the state to be presumed a South Carolina resident for individual income tax purposes.' Residency turns entirely on domicile. | 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 | S.C. Code § 12-6-30(2) defines a resident individual as 'an individual domiciled in this State.' Domicile itself is undefined in the tax code and comes from case law: South Carolina courts (Phillips v. South Carolina Tax Commission, 195 S.C. 472, 12 S.E.2d 13 (1940); Gasque v. Gasque, 246 S.C. 423, 143 S.E.2d 811 (1965); Ravenel v. Dekle, 265 S.C. 364, 218 S.E.2d 521 (1974)) define domicile as the place a person has a true, fixed, and permanent home and principal establishment, to which they intend to return whenever absent. Intent is the most important element, evaluated against conduct: the Department's published Domicile Guide (June 2021) lists non-exhaustive factors grouped as property (deeds, real property, motor vehicles, the 4% assessment ratio), employment and financial (where wages are earned, where taxes are paid, bank account and bill addresses), licenses and registrations (voter registration, driver's license, vehicle registration, professional licenses), family (where spouse and dependents live), and affiliations (civic ties, place of worship, professional service providers). No single factor is dispositive. | 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 | No fixed threshold | 270 days |
| Any Part of a Day Rule | Not applicable; South Carolina has no statutory day-count test. A nonresident who works in South Carolina or spends winter months there does not automatically become a South Carolina resident, and conversely a domiciled South Carolina resident who is physically absent for months or years remains a resident if they intend to return. | 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 | Military servicemembers who entered service while domiciled in South Carolina are presumed to remain South Carolina residents for tax purposes unless they affirmatively establish legal residence elsewhere and abandon South Carolina domicile (S.C. Regulation 117-640.2). No general civilian day-count presumption exists. | 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 South Carolina
South Carolina Administrative Law Court decisions (F. Abbott Brown v. Charleston County Assessor, 03-ALC-17-0515 (2004); D. Bradlee Hodson v. Charleston County Assessor, 01-ALJ-17-0286 (2001); Floyd v. South Carolina Department of Revenue, 15-ALJ-17-0458-CC (2016), aff'd per curiam 2019 WL 141503 (S.C. Ct. App. 2019)) show the Department and county assessors testing domicile changes primarily through the 4% legal-residence property tax assessment ratio and DOR residency determinations, weighing driver's license, voter registration, vehicle registration, and filed tax returns against actual conduct and stated intent. In each cited case the taxpayer prevailed despite missing one or more of the standard documents, because the courts held that documents are evidence of intent, not a checklist requirement.
Trailing Income
Because South Carolina taxes residents on all personal service income regardless of source but does not tax nonresidents' worldwide business income, the trailing exposure after leaving is narrower than in states with full worldwide-income taxation: a departed resident still owes South Carolina tax on South Carolina-source personal service income and the apportioned South Carolina share of business income, but not on wages earned entirely outside the state after a genuine domicile change.
Part-Year Filing
A part-year resident (S.C. Code § 12-6-30(3): 'an individual who is a resident individual for only a portion of the tax year') files Form SC1040 and generally has the option to file as a full-year resident claiming credit for taxes paid to other states (Form SC1040TC), or to file SC1040 with Schedule NR reporting only income earned while a South Carolina resident plus any South Carolina-source income earned as a nonresident, prorating deductions.
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
South Carolina Top Rate
6%
Idaho Top Rate
5.30%
Moving from South Carolina to Idaho drops the top marginal income tax rate from about 6% to about 5.3%, a reduction of roughly 0.7 percentage points.
Withholding Reciprocity
South Carolina 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
South Carolina 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
South Carolina
Capital gains: Taxed as South Carolina income; a 44% deduction is generally available against net long-term capital gains for state purposes, which is the state's primary capital-gains relief mechanism rather than a separate lower rate.
Estate or inheritance tax: None. South Carolina has no estate tax and no inheritance tax.
Property tax: South Carolina's owner-occupied primary residence qualifies for the 4% legal-residence assessment ratio under S.C. Code § 12-43-220(c) instead of the standard 6% ratio, a major property tax reduction tied directly to domicile; a separate Homestead Exemption for owners 65+, totally and permanently disabled, or legally blind exempts the first $50,000 of fair market value from tax entirely, but only after residing in South Carolina as a permanent home for a full prior calendar year.
Sales tax: 6% state rate, with local option taxes pushing the average combined state-and-local rate to about 7.49%.
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 South Carolina
South Carolina's large hospital systems (MUSC in Charleston, Prisma Health, McLeod) make it a significant travel-nurse assignment market. Because South Carolina has no day-count residency trigger, a nurse working consecutive South Carolina contracts is not automatically pulled into residency the way they would be in a 183-day state; the exposure runs through South Carolina's domicile test instead, meaning a nurse who buys a home, registers to vote, or otherwise shows intent to make South Carolina permanent can become domiciled regardless of the nominal 'tax home' claimed 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 South Carolina
Charleston and Greenville host minor-league and college sports rather than a major-league franchise, so South Carolina's jock-tax exposure is almost entirely on the visiting-player side: nonresident athletes on teams playing in South Carolina owe apportioned South Carolina tax on the personal-service income allocated to South Carolina duty days, following the state's general rule taxing nonresidents on South Carolina-source personal service income.
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 South Carolina
Because South Carolina runs no day-count test, a snowbird can spend an extended winter in South Carolina without becoming a resident, as long as they do not develop the intent to make South Carolina their permanent home; the Department's own guidance states a nonresident spending winter months in South Carolina does not automatically become a South Carolina resident. The risk flips for someone who buys a South Carolina home, joins clubs, opens local bank accounts, and gradually shifts their center of life there, as in Brown, where the taxpayer was found domiciled in South Carolina despite lacking a South Carolina driver's license or vehicle registration that year.
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 South Carolina
South Carolina has no convenience-of-the-employer rule. A remote worker physically performing work from South Carolina owes South Carolina tax on that personal service income (since South Carolina taxes residents' personal service income regardless of source and nonresidents' South Carolina-source personal service income), and the credit for taxes paid to other states (Code § 12-6-3400) is the mechanism for avoiding double taxation if the employer's home state also asserts a claim.
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 South Carolina
South Carolina follows the federal Servicemembers Civil Relief Act, the Military Spouses Residency Relief Act, and the Veterans Benefits and Transition Act: a servicemember does not lose or acquire South Carolina domicile solely by being present or absent under military orders, and a spouse may elect to use the servicemember's state of residence for tax purposes regardless of when the marriage occurred. Under S.C. Regulation 117-640.2, a servicemember who entered service while domiciled in South Carolina is presumed to remain a South Carolina resident for tax purposes unless they affirmatively establish a new domicile and abandon South Carolina, even if the new state (like Texas or Florida) has no income tax.
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 South Carolina
Charlotte Douglas (just across the North Carolina line) and smaller in-state airports mean some airline crew live in South Carolina while based elsewhere. Federal law (49 U.S.C. § 40116) limits state taxation of air carrier employees to their state of residence and, narrowly, a state where more than 50% of pay is earned; crew domiciled in South Carolina are taxed on personal service income under the state's standard resident rules.
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
South Carolina to Idaho FAQ
Does South Carolina have a 183-day rule like New York or California?+
No. The South Carolina Department of Revenue states directly that, unlike states with a day-count presumption such as 183 days, South Carolina has no minimum time that must be spent in the state to be presumed a resident. Residency depends entirely on domicile: where your true, fixed, permanent home is and where you intend to return when away.
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 bought a house in South Carolina but haven't gotten a South Carolina driver's license or registered to vote yet. Am I still a resident?+
Possibly yes. In F. Abbott Brown v. Charleston County Assessor, the taxpayer was found domiciled in South Carolina for a full year despite having none of those three documents, because the court found his conduct, joining a local club, banking locally, moving into the home with intent to stay, demonstrated domicile regardless of the missing paperwork. The Department's own guidance says intent and conduct control, not any single document.
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's the difference between South Carolina's homestead exemption and the 4% assessment ratio?+
They're two different benefits. The 4% legal-residence assessment ratio applies to any owner-occupant whose South Carolina home is their domicile, cutting the property tax assessment ratio from 6% to 4%, and is available immediately. The Homestead Exemption is narrower: it exempts the first $50,000 of fair market value entirely, but only for owners who are 65 or older, totally and permanently disabled, or legally blind, and only after a full prior calendar year of South Carolina residency.
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 moved to Wyoming for a few years and never got a Wyoming driver's license. Did I stay a South Carolina resident?+
Not necessarily. In Floyd v. South Carolina Department of Revenue, a taxpayer who moved to Wyoming without ever obtaining a Wyoming license or registering to vote there was still found to have abandoned South Carolina domicile, because the court credited her testimony that she genuinely intended to build a life in Wyoming. Missing documents hurt your case but are not automatically fatal if your actual conduct and credible intent point 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.
Does Social Security get taxed once I retire in South Carolina?+
No. South Carolina fully exempts Social Security benefits, and on top of that offers a $10,000 per-person retirement income deduction at age 65 and older ($3,000 under 65) that applies to pensions, 401(k)s, and IRA distributions.
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.
How does South Carolina tax my income if I still work remotely for my old employer after moving here?+
South Carolina taxes residents on all personal service income (wages and self-employment earnings from labor) regardless of where it's earned, so your remote wages are taxable in South Carolina once you're domiciled here. If your former state also claims a right to tax the same income, South Carolina's credit for taxes paid to another state (Code § 12-6-3400) prevents double taxation.
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 South Carolina
Moving the other direction is a different fact pattern, not a mirror image: exit risk and establishment mechanics both flip.
View the Idaho to South Carolina guideAlso Consider, Leaving South Carolina
South Carolina to Idaho Reading
Reviewed Against 22 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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