Estimate the Capital Gains Tax due when you sell shares or other assets.
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What this calculator covers and how the numbers are worked out
Capital Gains Tax, or CGT, is charged on the profit you make when you sell or dispose of an asset that has increased in value, things like shares outside an ISA, a second property, or other valuable possessions. This calculator helps you estimate how much CGT you might owe on a gain, based on your income and the exempt amount everyone gets each year.
Every individual has a tax-free exempt amount for capital gains, £3,000 for the 2026/27 tax year. Any gain above that is what's actually taxed, gains within the £3,000 allowance are simply tax-free and don't need to be paid on at all.
The rate you pay on gains above the exempt amount depends on your income, not just the size of the gain. For most assets, gains are taxed at 18% for the portion that falls within your remaining basic-rate band, and 24% for anything above that. This means the same £10,000 gain could be taxed very differently depending on how much other income you already have that year, because your other income uses up your basic-rate band first, before your gain is added on top.
Here's a worked example. Suppose your gross salary for the year is £42,570 — that's the figure to type into the calculator above, before any tax-free allowance is deducted. After your £12,570 Personal Allowance, your taxable income is £30,000, leaving £7,700 of your £37,700 basic-rate band unused (£37,700 minus £30,000). You then sell some shares and make a gain of £13,000. First, subtract the £3,000 exempt amount, leaving £10,000 of taxable gain. Of that £10,000, £7,700 fits within your remaining basic-rate band and is taxed at 18%, that's £1,386. The remaining £2,300 spills over into the higher-rate territory and is taxed at 24%, that's £552. Your total CGT bill would be £1,386 + £552 = £1,938.
If you're already a higher-rate taxpayer with no basic-rate band left, the whole of your taxable gain, after the £3,000 exemption, is taxed at 24%. There's no way around this by timing things differently within the same tax year, though some people do plan disposals across tax years to make the most of two separate £3,000 exempt amounts.
Your main home is usually completely exempt from CGT under something called Private Residence Relief, which covers a property you've lived in as your only or main home. This calculator is aimed at other assets, like investment property, shares, or valuable possessions, not the home you live in.
Losses matter too. If you've made losses on other asset sales, in the same tax year or carried forward from earlier years, you can offset them against your gains to reduce the amount that's taxable. The catch is that losses must be formally reported to HMRC to be used this way, even in a year where no tax is actually due, otherwise you may not be able to claim them later.
£3,000 per person. Any gain above that in the tax year is potentially taxable, but gains within the £3,000 are completely tax-free.
It depends on your total income (enter your gross salary or other income before tax) plus the gain. The portion of the gain that fits within your remaining basic-rate band is taxed at 18%; anything above that is taxed at 24%.
Usually not. Private Residence Relief exempts a property that's been your only or main home for the whole time you've owned it, from CGT.
Yes, losses on other asset disposals in the same tax year or carried forward from earlier years can be offset against your gains. They must be reported to HMRC to be used, even if no tax is due that year.
Then you likely have no basic-rate band left, so the whole of your taxable gain above the £3,000 exempt amount is taxed at 24%.
Each of you has your own separate £3,000 exempt amount rather than a shared pot, but assets can usually be transferred between spouses or civil partners tax-free, which some couples use to spread a gain across two allowances.
You don't need to pay tax on them, but it's still worth keeping records. If you've made a loss instead, you should report it to HMRC to preserve your ability to use it against gains in future.
Common examples are shares and funds held outside an ISA, second homes and buy-to-let property, and other valuable possessions, but not your main home, which is usually covered by Private Residence Relief instead.
For most disposals other than UK residential property, it's reported and paid through Self Assessment for the relevant tax year. If you sell UK residential property (and it's not fully covered by Private Residence Relief), you must report the gain and pay the CGT within 60 days of completion, using HMRC's separate property disposal reporting service — that's much sooner than the usual Self Assessment deadline.
These results are estimates for general guidance and are not financial advice. Always confirm important figures with an official source.
Rates last reviewed: 2 October 2026 · Built around the 2026/27 UK tax year
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