What is the SA108 capital gains summary?
The SA108 supplementary pages record capital gains and losses on your SA100 tax return. You use them when you have sold or disposed of something that increased in value and you need to report it through Self Assessment. The Capital Gains Tax annual exempt amount for individuals is £3,000.
Figures checked against gov.uk on . General information, not tax advice.
When it applies
gov.uk lists having Capital Gains Tax to pay on a sale or disposal as one reason to send a return. Gains on UK residential property are different in one respect: for a sale completed on or after 27 October 2021, gov.uk says to report and pay within 60 days of the sale.
Other gains are normally reported on the return for the tax year after the sale, or through the real-time Capital Gains Tax service by 31 December in the tax year after the sale if you are eligible.
What you will need
For each disposal keep the dates, the proceeds, what you paid and any allowable costs. The annual exempt amount comes off your total gains before tax is worked out, so a small gain may produce no tax. gov.uk gives the annual exempt amount as £3,000 for individuals and £1,500 for trusts.
gov.uk's notes for the SA108 are the place to check any reporting threshold; the form page itself does not state one.