Capital gains tax on shares in 2026/27: rates, allowance and worked examples

Working out the gain on a share sale

The gain is what you sold for minus what you paid. You can deduct the costs of buying and selling — such as stockbrokers' fees, and the Stamp Duty Reserve Tax you paid when you bought (GOV.UK).

If you were given the shares (by someone other than your spouse, civil partner or a charity), or inherited them and don't know their Inheritance Tax value, you use their market value at that time as your cost.

Bought at different times? Use the average

When you sell shares of the same type in a company you bought in several lots, you usually work out the average cost of all of them. GOV.UK's own example: 100 shares at 80p (£80) and 300 at £1.20 (£360) make 400 shares costing £440 — an average of £1.10. Sell 150 and their cost is £165 (GOV.UK).

The 30-day rule. If you buy shares of the same type in the same company within 30 days of selling, special rules decide which purchase is matched with the sale, so the average doesn't apply in the usual way. HMRC's helpsheet HS284 sets them out. In short: selling to use your allowance and buying straight back doesn't reset your cost the way you might expect.

Worked examples

A basic-rate taxpayer on £30,000 with a £10,000 gain

After the £3,000 allowance, £7,000 is taxable. It all fits in the unused basic-rate band, so it's taxed at 18%: £1,260.

A higher-rate taxpayer on £60,000 with the same gain

No basic band is left, so all £7,000 is at 24%: £1,680.

On £45,000 with a £20,000 gain — split across the bands

£17,000 is taxable. £5,270 fits in what's left of the basic band at 18%, and £11,730 is at 24% — £3,764 in total, an effective 19% of the whole gain.

Using losses

An £8,000 gain and a £5,000 loss in the same year net to £3,000, which the allowance covers: £0 to pay. Losses from earlier years only need to bring gains down to the allowance — on a £12,000 gain, £9,000 of a £20,000 brought-forward loss is used and the rest carries forward.

Try your own sale in the capital gains tax calculator — it uses the same engine.

A full example: several purchases, fees and a partial sale

Say you built up a holding in one company over three years, then sold part of it. These figures are illustrative; the method is the average-cost approach GOV.UK describes.

The average cost is £15,530 ÷ 3,000 = £5.18 a share. You sell 2,000 shares for £21,000 and pay £10 in dealing fees. Their cost from the pool is £10,353, so the gain is £21,000 − £10,353 − £10 = £10,637.

On a £50,000 salary, after the £3,000 allowance £7,637 is taxable: £270 at 18% and £7,367 at 24% — £1,817. The 1,000 shares you kept stay in the pool at the same average cost for the next sale.

Keep the contract notes for every purchase and sale. Without them, rebuilding the average years later is guesswork — and the fees you can deduct are easy to lose.

CGT on a share gain at different salaries

Tax on a single share gain in 2026/27, assuming no other gains or losses, the full Personal Allowance, and income from salary only:

Legitimate ways to pay less

• Use your ISA allowance. Gains inside an ISA aren't taxed, so new money invested there never creates a CGT bill.
• Use the £3,000 allowance each year. Spreading sales across tax years can keep each year's gains under the allowance — mind the 30-day rule if you buy back.
• Claim your losses. Losses can be set against gains, and unused ones carried forward.
• Gifts between spouses and civil partners usually aren't taxed — worth knowing before you decide who in a household sells.

Reporting and paying

If your total taxable gains are above your allowance, you need to report and pay (GOV.UK):

• On a Self Assessment return for the tax year after the sale, or
• Through the real-time CGT service (UK residents), reporting by 31 December after the end of the tax year and paying by 31 January — so a gain in 2026/27 is reported by 31 December 2027 (GOV.UK). If you're already in Self Assessment, include the sale on your return too.

Selling UK residential property is different: it has its own 60-day reporting deadline.

Common mistakes

• Taxing the sale price instead of the gain. Only the profit is taxed, after costs.
• Treating the allowance as per sale. £3,000 covers all your gains in the year combined.
• Ignoring income. A big salary or bonus uses up the basic band and pushes gains to 24%.
• Selling and buying straight back. The 30-day rule means this doesn't reset your cost.
• Forgetting old losses. Unclaimed losses from previous years can reduce this year's bill.