Capital Gains Tax on Shares Calculator

Work out exactly how much Capital Gains Tax (CGT) you owe when you sell shares, funds or units held outside an ISA or pension. Updated for the 2025/26 tax year with the latest HMRC figures: the £3,000 annual exempt amount and the 18% and 24% CGT rates that apply to disposals from 30 October 2024. The calculator splits your gain across the part of your basic-rate Income Tax band that is still unused (taxed at 18%) and the rest (taxed at 24%), exactly as HMRC requires.

Understanding CGT on Shares in 2025/26

Capital Gains Tax on shares is charged on the profit you make when you dispose of shares, investment funds or units that are held outside a tax-protected wrapper. A "disposal" includes selling shares, giving them away, or swapping them for something else. Crucially, you are taxed only on the gain — the difference between what you received and what you paid — not on the full sale value. For the 2025/26 tax year, the rules tightened again, with a much smaller tax-free allowance and the higher main rate sitting at 24%.

The biggest change came on 30 October 2024, when the Chancellor raised the main CGT rates from 10% and 20% to 18% and 24% with immediate effect. Because the change applies to disposals on or after that date, it covers the entire 2025/26 tax year (6 April 2025 to 5 April 2026). These are now the same headline rates that apply to residential property gains, although shares no longer carry the old 28% top rate that property briefly did.

CGT Rates on Shares 2025/26

The rate you pay is not decided by your income alone — it depends on how the taxable gain stacks on top of your income. The taxable gain is treated as the top slice of your total taxable amount for the year. The portion that still fits inside the basic-rate band (which runs up to £50,270 for England, Wales and Northern Ireland) is taxed at 18%; anything above it is taxed at 24%. This is exactly the band split this calculator performs for you.

The £3,000 Annual Exempt Amount

Every UK individual has an annual exempt amount (also called the CGT allowance) of £3,000 for 2025/26. You can make total chargeable gains up to this amount across all your assets in the tax year without paying any CGT. This allowance has been cut sharply in recent years: it was £12,300 in 2022/23, fell to £6,000 in 2023/24, and was halved again to £3,000 from 2024/25. The allowance cannot be carried forward — if you do not use it in a tax year, it is lost.

The exempt amount is applied after deducting allowable costs and any capital losses, and it is used against your total gains for the year. If you have gains on shares and on another asset such as a second property, you choose how to allocate the allowance — sensibly, you would set it against the gain taxed at the highest rate first.

How the Share Gain is Calculated

HMRC uses a clear formula for ordinary share disposals. The chargeable gain is your proceeds minus the cost of acquiring the shares and minus the incidental costs of buying and selling them:

Allowable incidental costs include broker dealing commission on both the purchase and the sale, and the 0.5% Stamp Duty Reserve Tax you paid when buying UK shares electronically. They do not include ongoing platform or subscription fees. Where you have bought the same shares on different dates, HMRC's "Section 104 pooling" and "same-day" and "30-day (bed-and-breakfast)" matching rules determine the average cost — for a single holding bought once, the cost is simply what you paid.

Worked Example: Selling Shares Worth £40,000

Suppose Sarah, a basic-rate taxpayer, sells shares in a FTSE 100 company in November 2025. She receives £40,000 in proceeds, the shares originally cost her £22,000, and she paid £150 in dealing fees and stamp duty across the buy and sell. Her taxable income (after the personal allowance) for 2025/26 is £35,000. She has no other gains and no losses to bring forward.

1. Gain: £40,000 − £22,000 − £150 = £17,850
2. Annual exempt amount: £17,850 − £3,000 = £14,850 taxable gain
3. Remaining basic-rate band: £50,270 − £35,000 = £15,270 of unused band
4. Band split: The whole £14,850 fits inside the £15,270 of remaining band, so all of it is taxed at 18%
5. CGT due: £14,850 × 18% = £2,673

Sarah's effective rate on her total £17,850 gain is about 15% once the tax-free allowance is taken into account. Now imagine her income were £45,000 instead. Her remaining band would be only £5,270, so £5,270 of the gain would be taxed at 18% (£948.60) and the remaining £9,580 at 24% (£2,299.20), giving total CGT of £3,247.80. The same gain costs over £570 more simply because more of it spills into the higher rate band — which is exactly why timing disposals around your income matters.

The Factors That Affect Your Share CGT Bill

Your Income Decides the Band Split

Because the taxable gain sits on top of your income, two people with identical gains can owe very different amounts of tax. A retiree with a £15,000 pension has most of their basic-rate band free, so a large share of the gain is taxed at 18%. A salaried higher-rate taxpayer earning £70,000 has no band left at all, so the entire taxable gain is charged at 24%. Pension contributions in the same year extend your basic-rate band and can pull more of a gain into the 18% rate.

Spouse Transfers and Doubling the Allowance

Transfers of shares between spouses and civil partners who live together are made on a "no gain, no loss" basis and are free of CGT. By transferring some shares to a partner before selling, a couple can use two £3,000 allowances (£6,000 in total) and, if one partner is a basic-rate taxpayer, shift part of the gain to the 18% rate. This is one of the simplest and most effective ways to cut a CGT bill legally.

Bed and ISA / Bed and Spouse

"Bed and ISA" means selling shares held in a taxable account and immediately rebuying the same shares inside a Stocks & Shares ISA. The sale crystallises a gain that uses up your annual allowance, but from then on all future growth and dividends are sheltered from CGT and Income Tax. The 2025/26 ISA allowance is £20,000. Spreading large disposals across two tax years (selling some shares on 5 April and the rest on 6 April) lets you use two years' worth of the £3,000 allowance.

Offsetting and Carrying Forward Losses

If you sell some shares at a loss, that loss is first set against your gains in the same tax year. Any unused loss is carried forward indefinitely and used against future gains, but only down to the level of the annual exempt amount in later years. Losses must be claimed by reporting them to HMRC within four years of the end of the tax year in which they arose, even if no tax is due, so that they are preserved.

Reporting and Paying the Tax

Unlike residential property — which has a 60-day reporting deadline — gains on shares are usually reported through your annual Self Assessment tax return after the end of the tax year. You must report if your total proceeds exceed a reporting threshold or your gains exceed the annual exempt amount. HMRC also offers a "real time" Capital Gains Tax service for those not in Self Assessment. The tax is due by 31 January following the end of the tax year.

Share CGT vs Dividend Tax — A Quick Comparison

Investors often hold both: dividends are taxed each year as they are received, while CGT only bites when you sell. If you want to model the income side, use our dividend tax calculator alongside this tool.

Frequently Asked Questions

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