Selling investments in 2025/26: reconstruct the disposal record before calculating Capital Gains Tax.

1. Start with every account, not the tax certificate

List each taxable brokerage, investment platform, certificated holding and investment club interest used during 6 April 2025 to 5 April 2026. Keep ISAs and pensions separate. Obtain the raw transaction history as well as the annual summary, because transferred holdings and corporate actions may not be fully reflected in a platform’s gain figure.

Combine accounts belonging to the same person. UK share identification is not performed separately for each broker. A purchase through one platform can affect the matching of a sale through another.

2. Identify disposals before calculating gains

Record sales, gifts, exchanges, redemptions and other events that may be disposals, with the contract or transaction date, quantity and gross proceeds. A movement between your own accounts is not itself a disposal, but preserve the transfer trail and original acquisition history.

Reconcile cash proceeds after fees back to the gross transaction. If shares were transferred to a spouse or civil partner, gifted to someone else or sold to a connected person, do not assume the cash amount is the tax value. The relationship, ownership and market-value rules need review.

3. Reconstruct allowable cost and corporate actions

For each holding, trace purchases, dealing costs and relevant corporate actions. Rights issues, takeovers, demergers, share reorganisations, distributions and reinvestment plans can alter the number of shares or pooled cost without appearing as an ordinary purchase.

Do not use the current platform book cost automatically where shares were inherited, gifted, moved between brokers or acquired through employment. Keep probate values, gift documentation, option or award statements, payroll records and any previous tax elections with the calculation.

4. Apply UK share matching in the correct order

For shares of the same class in the same company held in the same capacity, a disposal is generally matched first with acquisitions on the same day, then with qualifying acquisitions in the following 30 days, before the balance is matched to the Section 104 holding. The pool tracks the quantity and aggregate allowable expenditure.

This means first-in, first-out calculations and some broker reports can be wrong for UK tax. Create one dated chronology across all taxable accounts before updating the pool. Reconcile the closing pool so it can be carried forward to later years.

5. Separate gains, losses and special claims

Calculate each disposal before offsetting allowable capital losses. Check current-year losses, valid brought-forward losses and any claims needed for assets that have become of negligible value. Share Loss Relief against income has additional conditions and should not be assumed merely because unlisted shares failed.

HMRC states that capital losses can generally be claimed up to four years after the end of the tax year of disposal. Keep the computation and evidence even where the loss is not used immediately.

6. Check both gains and disposal proceeds

For 2025/26, the individual annual exempt amount is £3,000. A person already within Self Assessment may still have to complete the capital-gains pages where total disposal proceeds exceed £50,000, even if taxable gains are below the allowance. Reporting requirements and tax payable are separate tests.

The SA108 return distinguishes listed shares and securities from unlisted shares and other asset categories. Reconcile disposal counts, proceeds, allowable costs, gains and losses to the supporting schedule rather than entering only the final taxable amount.

7. File the calculation and retain the evidence

For investment disposals reported through Self Assessment, the normal online filing and payment deadline for 2025/26 is 31 January 2027. The separate UK property reporting timetable does not replace the investment-disposal entries. HMRC says personal Capital Gains Tax records must generally be kept for at least one year after the Self Assessment deadline, with longer periods for late returns or enquiries. Retain acquisition and pool records for as long as later disposals may depend on them.

UA Tax supports investors in London and across the UK. Personal tax services start from £400; historic pool reconstruction, valuations and specialist relief claims may require a separately agreed scope. Get in touch with the tax year, brokers, approximate transaction count and whether historic acquisition records are available. We will confirm the scope and fee before work begins.

Official sources and further reading

These primary sources support the framework above. Check the current version before acting because tax law and HMRC guidance can change.

• GOV.UK: work out whether Capital Gains Tax is due
• HMRC: 2025/26 Capital gains summary and notes (SA108)
• HMRC: shares and Capital Gains Tax helpsheet HS284
• HMRC: share identification and Section 104 holdings
• GOV.UK: Capital Gains Tax allowances
• GOV.UK: report and pay Capital Gains Tax
• GOV.UK: Capital Gains Tax record keeping
• GOV.UK: reporting capital losses