For investments outside an ISA, a sale can create a gain or loss even if you reinvest the proceeds. Keep acquisition history, disposals, fees and corporate actions across relevant accounts. An app’s profit figure is not automatically the gain calculated under UK tax rules.
Identify the account and the disposal
Shares held in an ISA generally have different treatment from taxable holdings. Obtain trade confirmations showing dates, quantities, proceeds and charges, together with the account type. A disposal can also arise from certain gifts or transactions other than an ordinary sale.
Transfers between your own investment accounts should be explained so the accountant does not treat every movement as a sale. Corporate actions and employee share arrangements can require additional records.
Purchase history matters
UK share-matching rules can involve acquisitions on the same day, purchases within the following 30 days and a pooled holding. Selling through one broker does not necessarily mean only that broker's purchases are relevant.
For example, if you sell shares in one account and buy the same shares shortly afterwards in another taxable account, the transactions may interact. A platform's isolated profit figure may not reflect the correct UK matching calculation.
Consider the whole year's gains and losses
The annual exempt amount for an individual is £3,000 for 2025/26, subject to the applicable rules. Reporting can still be required in some circumstances even where there is no tax to pay. Other disposals and allowable losses need considering together.
Do not apply a single capital gains rate without checking the year, asset type and your wider taxable income. A dividend payment is income and should not be confused with a gain on disposing of the shares.
Prepare a complete file
Supply all relevant broker reports, historic acquisition costs, previous pooling calculations, corporate-action documents and loss records. Explain any missing history before the return is prepared.
TaxSimba can confirm whether the investment calculations fit the selected service. Complex share schemes, substantial transaction histories or foreign reporting may need additional work, which should be agreed before relying on a standard tax-return price.
Recover acquisition history before trusting the app gain
Illustrative preparation example.
An investment account shows sale proceeds but the shares were transferred in from another broker. Obtain the earlier acquisition and corporate-action records. The new app may not hold the history required for a UK tax calculation.
Check: Can the disposal be traced to the full relevant holding history across accounts?
| Check | Practical action |
|---|---|
| Which account and asset were disposed of? | Keep confirmations showing account type, dates, quantities, proceeds and charges. |
| Are matching acquisitions elsewhere included? | Provide all relevant broker histories and prior pool calculations. |
| What other gains or losses occurred? | Review the complete tax year and reporting conditions rather than one transaction alone. |
Can I use the app's displayed gain without checking?
Not safely where history, other brokers or UK matching rules are missing. Provide the underlying transactions.
Are dividends included in the capital gain?
They are a separate income item. Keep dividend statements distinct from disposal proceeds and acquisition costs.
Download a checklist for this guide
- Collect all relevant broker trade confirmations.
- Identify ISA and taxable accounts.
- Locate acquisition costs and pool workings.
- Record corporate actions and matching purchases.
- List other gains, losses and reporting questions.