US Capital Gains Tax Calculator 2026

Long-term gains on assets held for more than a year are taxed at 0%, 15% or 20% depending on your taxable income. For 2026 the 0% rate applies up to $49,450 of taxable income for single filers and $98,900 for joint filers, the 15% rate runs to $545,500 and $613,700 respectively, and the 20% rate applies above that. Short-term gains on assets held for a year or less are taxed as ordinary income at rates up to 37%.

The holding period is measured from the day after you acquire the asset to the day you dispose of it. More than one year makes the gain long-term and eligible for the preferential 0%, 15% and 20% rates. One year or less makes it short-term, taxed at your ordinary income rate. For a top-bracket taxpayer the difference between 37% and 20% on the same profit is substantial, so a disposal falling a few days either side of the anniversary is worth checking before you sell.

The Net Investment Income Tax is a 3.8% charge under section 1411 on the lesser of your net investment income and the amount by which your modified adjusted gross income exceeds a threshold. The thresholds are $200,000 for single and head of household filers, $250,000 for joint filers and $125,000 for married filing separately. They are set in the statute and are not adjusted for inflation, so more taxpayers are caught every year.

Yes. US citizens and resident aliens are subject to it wherever they live; only nonresident aliens are outside its scope. This surprises many Americans overseas, who reasonably assume that living and paying tax in another country removes them from a tax badged as a domestic health-care levy. It does not.

No, and this is the trap this calculator is built to show. For section 1411 purposes your modified adjusted gross income is your adjusted gross income increased by the amount excluded under section 911, net of any disallowed deductions. The excluded salary is therefore added straight back when the threshold is tested. Someone excluding the full $132,900 for 2026 can appear to have modest US income yet still be pushed over $200,000 and taxed at 3.8% on their gains.

Generally no. Foreign income tax credits under sections 27(a) and 901(a) may not be used to reduce your NIIT liability, because the credit operates against chapter 1 tax while the NIIT sits in chapter 2A. This is the single most important point for Americans in the UK: you can pay UK capital gains tax at 24%, wipe out your US income tax on the same gain with the credit, and still owe the 3.8% in full. Some taxpayers have argued for treaty-based relief, but that is a position to take advice on rather than assume.

You can. Where you elect to deduct foreign income taxes rather than claim them as a credit, some or all of that deduction may be allowed against net investment income, which reduces the NIIT base. The trade-off is that you lose the credit against your regular US income tax, which is usually worth far more. Modelling both routes is worthwhile in a year with large gains and little other foreign tax.

For 2026/27 the UK charges capital gains tax at 18% on gains falling within the basic rate band and 24% above it, after the annual exempt amount of £3,000. The residential and non-residential rates are now aligned, so the same figures apply to a rental property and to a share portfolio. Gains stack on top of your income, so a higher-rate earner pays 24% on effectively the whole gain.

Both countries can tax the same gain, but relief is available so that you are not left paying the full amount twice. In broad terms the foreign tax credit lets the US tax on the gain be reduced by the UK tax paid on it. Because UK rates on gains are usually the higher of the two, the credit often covers the US income tax in full. The residue that survives is the 3.8% NIIT, which no credit reaches.

Order matters for the credit. Where the UK has the primary taxing right, UK tax is paid first and then credited against the US liability on the same income. Sourcing rules complicate this for share sales, because section 865 generally sources gains on personal property by the residence of the seller, and a US citizen can be treated as a US resident for that purpose. The treaty can re-source the gain so the credit works, but that is a filing position that needs to be taken deliberately.

Losses offset gains of the same kind first, then the other kind. Where losses exceed gains, up to $3,000 a year ($1,500 if married filing separately) can be set against ordinary income, and anything left is carried forward indefinitely. This calculator applies losses to short-term gains first because those are taxed at the highest rate, then to long-term gains, and shows any carryforward separately.

If you sell at a loss and buy the same or a substantially identical security within 30 days before or after the sale, the loss is disallowed and added to the basis of the replacement holding. It is deferred rather than lost. Americans in the UK need to watch this alongside the UK bed-and-breakfasting rules, which work on a similar 30-day principle but with different mechanics, so a trade can fall foul of one regime and not the other.

When you sell a rental property, the part of the gain that reflects depreciation you claimed is taxed at ordinary rates capped at 25%, rather than at the normal long-term rates. It is a common and expensive surprise for landlords who expected 15% or 20% across the whole gain. Entering the depreciation figure in this calculator applies the cap correctly rather than assuming a flat 25%.

Section 121 lets you exclude up to $250,000 of gain, or $500,000 on a joint return, where you have owned and used the property as your main home for two of the previous five years. It applies to a home abroad as well as one in the United States. The wrinkle for Americans in the UK is that the UK gives full relief on a main residence through private residence relief, so the US exclusion may cap out and leave a taxable US gain on a property that is entirely free of UK tax, with no foreign tax to credit against it.

They can. Gains are computed in dollars, so the basis and the proceeds are each translated at the rate on the relevant date. A property bought when sterling was strong and sold when it was weak can produce a dollar gain that looks nothing like the sterling profit, and occasionally a dollar gain on a sterling loss. Where a foreign currency mortgage is repaid, a separate section 988 gain can also arise.

Yes, qualified dividends are taxed at the same 0%, 15% and 20% rates as long-term capital gains and stack in the same way. Dividends from UK companies are generally qualified because of the US-UK treaty. They also count as net investment income for the 3.8% charge, so a portfolio of UK shares can generate a NIIT liability without any disposal at all.

Possibly, depending on the state and on whether you have genuinely broken residency. Most states tax gains as ordinary income and a handful do not tax them at all. Moving abroad does not automatically end state residency, and the sticky states will keep taxing you until you can demonstrate a change of domicile. Anyone planning a large disposal after leaving the United States should settle their state position before the sale, not after.

Tax on gains is not withheld, so it is paid through quarterly estimated payments. A significant disposal can create an underpayment penalty even where the return itself is filed and paid on time. Americans abroad are caught by this more often than most, because their income tax is usually covered by the exclusion or by credits and they have no habit of making estimated payments, yet the NIIT on a gain has to be funded in the quarter it arises.