Capital Gains Tax Calculator

Estimate the UK capital gains tax on selling shares or funds. 2026/27 rates. Educational only — not tax advice.

Your Inputs

Sale proceeds (£)

Original cost (£)

Your annual income (£)

Salary and other taxable income. Decides how much of the gain is taxed at 18% vs 24%.

CGT annual allowance (£)

2026/27 allowance is £3,000. Change it here if HMRC updates it.

How CGT on shares works

You pay Capital Gains Tax on the profit when you sell shares outside a tax wrapper — not on the total amount. The first £3,000 of gains each year is tax-free.

Above that, the rate is 18% if the gain sits in your basic-rate band and 24% above it (2026/27 rates for shares).

Illustrative estimate only, ignoring losses carried forward, part-disposals and share pooling. Not tax advice — check current HMRC rules.

Enter your sale proceeds and original cost to estimate the capital gains tax.

How to use this calculator

1Enter your sale proceedsThe total amount you received (or expect to receive) for selling the shares or fund.
2Enter the original costWhat you originally paid for them, including any dealing charges. For shares bought at different times, use the average (pooled) cost.
3Enter your annual incomeYour salary and other taxable income. This decides how much of the gain is taxed at the 18% basic rate versus the 24% higher rate.
4Check the allowanceThe 2026/27 annual CGT exempt amount is £3,000. The calculator applies it automatically; change it if HMRC updates the figure.
5Read the resultSee the taxable gain, the CGT due, the split across the 18% and 24% bands, and what you keep after tax.

What capital gains tax is

Capital Gains Tax (CGT) is a tax on the profit when you sell an asset — like shares or funds — for more than you paid, outside a tax-free wrapper.

You're taxed on the gain, not the total sale amount. If you bought shares for £10,000 and sold them for £25,000, the gain is £15,000 — and only the part above your annual allowance is taxable.

Crucially, gains inside a stocks and shares ISA are completely free of CGT. That's why long-term investors shelter as much as they can inside the ISA wrapper — see the difference with our ISA calculator.

How it's calculated (2026/27)

First, subtract the annual exempt amount (£3,000) from your total gain. Then the remaining taxable gain is taxed at one or two rates depending on your income:

Taxable gain = Total gain − £3,000 allowance
Taxed at 18% where it falls in your basic-rate band, and 24% above it

18% — the portion of the gain that sits within your remaining basic-rate band.
24% — the portion above the basic-rate band (i.e. higher- and additional-rate territory).
Your income is added first, so a higher salary pushes more of the gain into the 24% band.

Legal ways to reduce CGT

CGT is one of the more avoidable taxes for a patient investor. Common, entirely legitimate approaches:

Use your ISA — up to £20,000 a year grows and is sold completely free of CGT.
Use the annual allowance — realise up to £3,000 of gains tax-free each year (it doesn't carry forward).
"Bed and ISA" — sell holdings in a general account and rebuy them inside an ISA to shelter future gains.
Offset losses — losses on other investments can be set against your gains.
Spread disposals across tax years to use more than one annual allowance.

What this calculator does not cover

It's a clean estimate for a straightforward share or fund disposal. It does not handle carried-forward losses, part-disposals, the share-pooling rules for shares bought at different prices, residential property (taxed on a different timeline), or business asset disposal relief. For anything complex, or before acting, check the current HMRC guidance or speak to a tax adviser.

Frequently asked questions

How much is capital gains tax on shares in the UK?

For 2026/27, gains on shares above the £3,000 annual allowance are taxed at 18% where they fall within your basic-rate band and 24% above it. Your income is counted first, so higher earners pay 24% on most or all of the gain.

What is the capital gains tax allowance for 2026/27?

The annual CGT exempt amount is £3,000. You can realise up to £3,000 of gains each tax year without paying any CGT. The allowance does not carry forward — if you don't use it, it's lost.

Do I pay capital gains tax in an ISA?

No. Gains on investments held inside a stocks and shares ISA are completely free of capital gains tax, no matter how large. This is one of the main reasons long-term investors use their ISA allowance every year.

How is the gain calculated?

The gain is your sale proceeds minus what you originally paid (plus allowable costs like dealing charges). For shares bought at different times, HMRC uses a pooled average cost. Only the gain above your annual allowance is taxable.

Can I use losses to reduce capital gains tax?

Yes. Capital losses on other investments can be offset against your gains in the same year, and unused losses can be carried forward to future years if reported to HMRC. This calculator does not include carried-forward losses.

When do I pay capital gains tax on shares?

CGT on shares is reported and paid through Self Assessment for the tax year in which you sold them, normally due by 31 January following the end of that tax year. Always check the current HMRC deadlines.

Keep more of your gains

Openbook helps you research and track UK shares — so you can plan disposals, use your allowances, and hold the right companies inside your ISA.

Screen UK stocks free

This calculator is for educational purposes only and does not constitute financial advice. Always do your own research or consult a regulated adviser before investing.