of which net investment income tax
An extra 3.8% on investment income above $200,000 of modified AGI single, $250,000 joint. It applies to the lesser of your net investment income and the amount over the threshold — so crossing by $100 costs $3.80, not 3.8% of the gain. Never indexed.
What if?
The same sale under different choices, each computed by the engine rather than estimated. Figures are the tax on the gain, so the rows stay comparable when a variant spans two tax years. Select one to load it into the calculator and read its full derivation.
Estimates only — this is not tax advice. Consult a CPA or enrolled agent before acting on these figures. The calculator does not model the alternative minimum tax, wash sales, like-kind exchanges, QSBS, installment sales, or state additions and subtractions. See what is out of scope.
Show your work — 0 steps, each with its rule and citation
How Idaho taxes a capital gain
Statutory authority: Idaho Code 63-3024(2) (retrieved 3 September 2026)
Idaho is not a flat-rate state, though it is usually described as one
Idaho is routinely listed alongside Colorado and Illinois as a flat-tax state, and for most purposes that is close enough. The statute is more specific. Idaho Code 63-3024(2)(a) imposes tax “at the rate of five and three-tenths percent (5.3%) of taxable income over two thousand five hundred dollars ($2,500)”, and paragraph (b) makes the figure $5,000 on a joint return.
So there is a band at the bottom taxed at nothing, and a single rate above it — the same two-band shape as Mississippi and Oklahoma rather than a true flat rate. For anyone with an ordinary income the band is used up long before a sale is considered, and the tax on a gain is simply 5.3% of it. For someone with almost no other income the band is real money.
One drafting detail that catches people out: a surviving spouse and a head of household are treated as filing jointly for this purpose, so both get the larger band. Married filing separately does not — a separate return falls under paragraph (a) and gets the single figure.
The 60% deduction is the trap on this page
Idaho grants a deduction of up to 60% of qualifying capital gain, which sounds like the most generous relief on this site and is nearly always irrelevant to the person reading about it.
It reaches Idaho property, and a specific list of it: real property held at least twelve months, tangible personal property used in a revenue-producing enterprise held twelve months, cattle and horses held twenty-four months, other breeding livestock held twelve months, and Idaho timber held twenty-four months. The holding periods differ by asset, and the property must be in Idaho.
What it expressly does not reach is intangible property. Stocks, bonds, and interests in partnerships, limited liability companies and S-corporations do not qualify, however long they were held. If you sold shares — the case this calculator opens with — the 60% deduction does nothing for you, and a calculator that applies it anyway will understate your Idaho bill by three fifths.
This calculator therefore assumes the deduction does not apply unless the asset is one it reaches, and says so in the working rather than silently omitting the line. If you are selling Idaho farmland or a rental, the deduction is real and large, and it is worth taking to someone who can confirm the asset qualifies.
Why this page carries last year’s band, and why that is safe
The $2,500 and $5,000 in the statute are not the figures anyone actually uses. Subsection (3) requires the Tax Commission to publish an annual factor that adjusts them for inflation against a 1998 base, so the operative thresholds move every year. For 2025 they were $4,811 single and $9,622 joint. The 2026 factor had not been published when this page was built — the Commission’s rate schedule ran from 2025 back to 2012 and named 2026 nowhere.
Ordinarily that stops a state being computed, and it is why several states on this site are verified but produce no figure. Idaho is different because of where the uncertainty sits. The tax a sale adds is the tax on your income with the gain less the tax without it, and where your other income already clears the band, the band appears on both sides of that subtraction and cancels exactly. The answer is 5.3% of the gain whatever the threshold turns out to be.
The threshold can only change the answer for someone whose income lands inside the band, and even then the error is bounded by 5.3% of one year’s inflation on it — single figures, not hundreds. That is a very different exposure from a state with four rate steps, where stale thresholds move which rate applies across a wide range of incomes. The calculator still warns that the figures are the 2025 ones, because a small avoidable error is still an error.
Idaho against the states around it
The Pacific Northwest is unusually varied on this question, so the comparison is worth more than it usually is.
Washington, next door, has no income tax at all and instead levies a 7% excise aimed specifically at long-term capital gains above a large annual exemption, with an extra 2.9% at the top — so a modest Washington gain costs nothing and a very large one can cost more than Idaho would take. Utah, to the south, applies a flat 4.5% with no band at all. Idaho sits between them at 5.3% on a base that starts a few thousand dollars up.
Nevada and Wyoming, also bordering Idaho, levy no individual income tax and have no page here; Oregon and Montana border it too and neither has been verified from a primary source, so neither is quoted. That is the honest limit of a regional comparison on this site — it can only include states whose figures have actually been read.
What Idaho does not change
None of this touches the federal calculation, which runs identically wherever you live: the preferential ladder for a long holding, the additional charge on investment income above a threshold, and the reliefs available on a main home or a depreciated rental. Idaho’s 5.3% is laid over that result.
The state figure approximates Idaho taxable income with federal ordinary taxable income. Idaho has its own additions and subtractions, its own treatment of retirement income, and the capital gains deduction discussed above, none of which are modelled beyond what is described here. The figure is close for a straightforward wage-and-sale year and rougher where a return carries state adjustments, and it assumes Idaho residency for the whole year.
A worked Idaho example
Every figure below is computed by the same engine that powers the calculator above, at the moment this page was built — not typed in by hand. When the tax-year data is updated, this example updates with it.
A $200,000 share sale, with no deduction
A single filer in Idaho earning $120,000 sells long-held shares for a $200,000 gain. Shares are intangible property, so Idaho’s 60% deduction does not apply.
- Taxable income after deduction
- $303,900
- Taxable gain
- $200,000
- Tax owed without the sale
- $17,570
- Tax the sale added
- $34,560
- of which net investment income tax
- $4,560
- Total federal tax
- $52,130
- Idaho state tax
- $10,600
- Effective rate on the gain
- 17.28%
The Idaho charge is 5.3% of the whole gain. The zero-rate band was consumed by salary long before the sale, which is why the unpublished 2026 threshold makes no difference to this figure at all.
Caveats on this example (3)
- Net investment income was derived from capital gains and qualified dividends only. Interest, non-qualified dividends, rents, royalties and passive business income inside ordinaryIncome are also net investment income under IRC 1411(c) and are not counted here.
- Idaho bracket thresholds are the 2025 figures; the 2026 amounts were not published when checked, so the Idaho figure will change once they are. The rate ladder itself is verified from Idaho Code 63-3024(2).
- Idaho: the state taxable income base is approximated by federal ordinary taxable income. State additions, subtractions and deductions are not modelled.
Show the working — 14 steps, each with its citation
- Net short-term capital gain or loss for the year$0
Assets held one year or less. Taxed at ordinary rates if a net gain.
- Net long-term capital gain or loss for the year$200,000
Assets held more than one year. Eligible for the 0/15/20% rates.
- Standard deduction-$16,100
Adjusted gross income of $320,000 less $16,100.
- Taxable income$303,900
The figure the rate tables and the capital gain ceilings are both measured against.
- Ordinary income taxed at 10%$1,240
$12,400 of taxable income between $0 and $12,400.
- Ordinary income taxed at 12%$4,560
$38,000 of taxable income between $12,400 and $50,400.
- Ordinary income taxed at 22%$11,770
$53,500 of taxable income between $50,400 and $103,900.
- Ordinary income stacked below the long-term gain$103,900
Long-term gain is taxed by reference to where it sits ON TOP of $103,900 of other taxable income, not from the bottom of the rate table.
- Long-term gain taxed at 15%$30,000
Gain between the $49,450 zero-rate ceiling and the $545,500 15% ceiling.
- Net investment income tax threshold$200,000
Modified AGI of $320,000 against the $200,000 threshold for a single filer. This threshold is statutory and is not adjusted for inflation.
- Net investment income tax at 3.8%$4,560
3.8% of $120,000, the lesser of net investment income ($200,000) and the amount by which modified AGI exceeds the threshold ($120,000). Here the binding figure is the excess of modified AGI over the threshold.
- Idaho: long-term gain subtraction does not apply$0
The gain does not meet the condition for the subtraction. Up to 60% of the gain on qualifying Idaho property: real property held at least 12 months, tangible personal property used in a revenue-producing enterprise held 12 months, cattle and horses held 24 months, other breeding livestock held 12 months, and Idaho timber held 24 months. Intangible property is excluded — stocks, bonds and partnership, LLC or S-corporation interests do not qualify.
- Idaho income tax on the gain$10,600
$200,000 stacked on $103,900 of other taxable income across a 2-bracket ladder topping out at 5.3%. Federal ordinary taxable income is used as the base; the state's own taxable income differs, so treat this as an approximation.
- Total tax$62,730
$62,730 on $320,000 of total income, an effective rate of 19.6%.
What this calculator does not cover for Idaho
The Idaho figure stacks your gain on your federal ordinary taxable income. Idaho computes its own taxable income with its own additions and subtractions, which are not modelled here — so treat the state number as a close approximation for a straightforward wage-and-sale situation, and as a rough one if your return carries significant state adjustments.
Full-year residency is assumed throughout. Part-year residents, non-residents, and gains sourced to property in another state all turn on rules this calculator does not model. The complete list of what is in and out of scope is on the methodology page.
Other states
- WashingtonNo income tax, but a 7% / 9.9% excise on long-term gains. Real estate exempt.
- UtahFlat 4.5%, with a non-refundable taxpayer credit not modelled.
See the full 2026 capital gains guide for the federal rules that apply wherever you live — the rate ladder, the net investment income tax, the home-sale exclusion and depreciation recapture — plus every state we currently cover.