Capital Gains on Shares 2026/27 | Pooling, Matching Rules & Reporting

Selling shares outside a tax wrapper can trigger Capital Gains Tax, but only on gains above your £3,000 annual exempt amount for 2026/27 — and only after HMRC's identification rules decide which shares you sold and at what cost. The rules that catch investors out are the Section 104 pooling rules, the same-day matching rule, and the 30-day bed and breakfasting rule, all designed to stop you cherry-picking acquisitions to manufacture a lower gain.

The £3,000 allowance is frozen at its 2024/25 level and has been cut twice in three years, so even modest portfolios now cross the threshold. Calculate gains accurately with the CGT Calculator→ before you trade, and plan tax-free repositioning with the Bed and ISA Calculator→.

The Basics: Rates and Allowance

Every individual has a £3,000 annual exempt amount for 2026/27; gains above it are taxed at 18% if they fall within your basic-rate band and 24% otherwise. Trusts have a £1,500 exempt amount. Shares and most funds — UK and overseas — use these rates from 6 April 2026; residential property has the same 18%/24% individual rates.

The exemption is per person, so a couple who transfer assets between themselves can shelter £6,000 of gains jointly. Because the allowance resets every 6 April, staggering sales across tax years is the single most effective way to reduce CGT on a growing portfolio.

Section 104 Pooling

Buy shares of the same class in the same company on different dates and HMRC pools them into one holding at an average cost per share. You cannot elect to sell the expensive shares and keep the cheap ones — every disposal uses the pool's average.

The sale of 200 shares at £10 uses a cost of 200 × £6 = £1,200, producing a gain of £800. The average cost is recalculated after every purchase, so keeping an up-to-date record of quantity, cost and average is essential — spreadsheet errors here are the most common cause of wrong CGT figures.

Same-Day and 30-Day Matching

Before the pool is touched, two matching rules apply. Same-day matching pairs a disposal with purchases of the same class made the same day, at their actual prices. 30-day matching then pairs the disposal with repurchases of the same class within the following 30 days — the bed and breakfasting rule that stops you crystallising gains or losses while staying invested.

Example: Ben sells 800 ABC shares at £12 on 15 March, then buys 300 at £11 on 20 March and 200 at £10.50 on 25 March. The 500 repurchased shares match the sale at their actual buy prices: £3,600 − £3,300 = £300 gain, and £2,400 − £2,100 = £300 gain. The remaining 300 shares come from his pool. If he had sold at £12 and waited 31 days to rebuy, the 30-day rule would not apply and the pool cost would set the gain — which is exactly why timing matters.

Worked Example: Anita's Pooled Sale

Anita bought 2,000 XYZ shares at £4 in June 2020 and 1,000 at £6 in March 2023, then sold 500 at £10 in August 2026. Her pool: 3,000 shares at £14,000 total, an average of £4.6667. The 500 sold use a cost of £2,333, against proceeds of £5,000, giving a gain of £2,667.

Anita's gain sits inside the exemption, so no CGT is due. The same trade a year later, after a further purchase and a sale of 800 shares, could easily exceed £3,000 — at which point the excess is taxed at 18% or 24% depending on her income band.

Losses and Reporting

Losses are the mirror image: they offset gains in the same year, are deducted before the exemption, and any unused balance carries forward indefinitely to future years. But a loss is disallowed if you buy the same shares back within 30 days — the repurchase adds the loss to the new shares' cost instead. Claim unused losses within four years of the end of the tax year, and report them on Self Assessment even if you have no gains to offset, so HMRC has them on record.

Where Self Assessment is the applicable route, report through the capital gains summary pages, listing each disposal's date, quantity, proceeds, cost and gain or loss. HMRC also provides other reporting routes in some circumstances. Shares inside an ISA never trigger CGT reporting — CGT simply does not apply there.

Shares vs Other Assets: Different Rules

Shares use the same individual CGT rates as residential property for 2026/27, but the identification rules are different. Residential property uses the same £3,000 exemption, has a 60-day reporting window for disposals, and has no pooling — each property is matched individually. Business assets may qualify for Business Asset Disposal Relief at a separate rate, subject to its conditions and limits, while personal possessions worth £6,000 or less may be exempt.

The practical takeaway: hold shares in ISAs where possible, use the £3,000 exemption deliberately each year, and keep property and business disposals in a separate planning track because their rates, reporting windows and reliefs differ sharply from share disposals.

Strategies to Keep Gains Tax-Free

• Use the ISA allowance — £20,000 a year of shares can grow and be sold free of CGT forever.
• Bed and ISA — sell within the £3,000 exemption and repurchase inside an ISA the next day; the 30-day rule does not apply to ISA repurchases.
• Transfer to your spouse — no-gain/no-loss transfers let a couple use two £3,000 exemptions and two ISA allowances.
• Stagger disposals — keep each tax year's gains under £3,000 by spreading sales across Aprils.
• Harvest losses — sell losing positions to offset winners, watching the 30-day rule on any repurchase.
• Consider your Income Tax band — pension contributions may change the band against which a gain is assessed, but they do not directly deduct a contribution from the capital gain.

Records and corporate actions

Keep contract notes, platform statements, dividend-reinvestment records, transfer documents, stock splits, takeovers, mergers and company reorganisations. A broker's current holding statement may show the number of shares but not the historic allowable cost needed for a Section 104 pool. Reconstruct the pool from acquisition records before selling, and record dealing fees and other allowable transaction costs separately from the cash paid.

Corporate actions can change the number, class or identity of shares without a simple purchase or sale. A consolidation, demerger, takeover or share exchange may require a specific tax treatment and a revised pool. Do not copy the broker's “average price” into a tax return without checking whether it includes non-taxable events or excludes earlier accounts. If records are missing, ask the platform or company registrar for historic information and document any reasonable reconstruction.

Employment shares, options, restricted stock and shares acquired through an employee plan may involve Income Tax or National Insurance before the later CGT calculation. The acquisition value for CGT may not be the amount originally paid, and a tax document from the employer can be important evidence. Keep the award, exercise, vesting and sale records together. This guide's ordinary-share examples should not be applied automatically to employment-related securities.

Before filing, reconcile proceeds, allowable costs, matched acquisitions, pool balance, losses and the annual exempt amount to the disposal dates. Apply the tax year in which the contract or disposal occurs, not simply the date money reaches the bank. Where a disposal is complex or involves a non-UK exchange, seek advice rather than using a generic calculator result as the filing figure.

Build the disposal schedule before selling

For each proposed sale, prepare a schedule with the security name and class, quantity, contract date, proceeds, dealing costs, acquisition pool, same-day purchases and any purchases in the following 30 days. Add the account wrapper and the tax year. This lets you see whether a sale is inside an ISA, whether the transaction is matched to a later acquisition and whether a loss can be claimed. Do not wait until the year-end statement if the sale involves several lots or a corporate action.

If you transfer shares between platforms, keep the original acquisition history. A new broker may show the transferred quantity but not the historic allowable cost or the matching transactions. Ask both platforms for contract notes and record the transfer date separately from a disposal. A transfer between your own accounts is not automatically a sale, but a change of ownership, gift or transfer to a spouse has its own consequences and evidence requirements.

Reporting is separate from calculating

Calculating a gain does not by itself answer whether a return or payment is due. Check the current HMRC reporting route, total disposal proceeds, taxable gains after losses and exemption, and whether you are already in Self Assessment. Keep a note of why a disposal was not reported as well as the return or payment reference when it was reported. If a loss is worth preserving, claim it even if no CGT is payable for the year; otherwise HMRC may not have it available for a later gain.

Review the schedule after the tax year ends. A later acquisition within 30 days can change the original matching calculation, and a corporate action can change the pool. Reconcile the final figures with the broker statement, HMRC submission and any amended return. This is particularly important for overseas shares, dividend reinvestment, employee shares and portfolios split across several platforms.

Frequently Asked Questions

Run every disposal through the CGT Calculator→ and plan tax-free repositioning with the Bed and ISA Calculator→. For the wider picture, read Capital Gains Tax 2026/27 and ISA Allowance 2026/27.

Official sources

• GOV.UK: Capital Gains Tax rates
• GOV.UK: Capital Gains Tax rates and allowances
• GOV.UK: If you make a loss
• GOV.UK: Work out if you need to pay
• GOV.UK: Reporting and paying Capital Gains Tax