Form SA108 – Fill, Sign and Download | Capital Gains Summary
ZenDocs is not a law firm and does not provide legal advice.
ZenDocs is not a law firm and does not provide legal advice.
Form SA108, the Capital Gains Tax summary, is the supplementary page attached to the main SA100 Self Assessment return for reporting gains and losses on assets you've sold or given away. It covers UK residential property that isn't your main home, shares and securities, cryptoassets, business assets, and other chargeable disposals such as valuable personal possessions worth more than £6,000 each.
You need it if the chargeable assets you disposed of were worth more than £50,000 in total, or if your chargeable gains before deducting any losses were more than the annual exempt amount of £3,000. You still need to complete it in either case even if no tax is actually due, for example because losses or reliefs bring your net position to nil, since HMRC still needs the underlying figures.
Since 6 April 2025, most chargeable gains are taxed at 18% within your basic rate band and 24% above it, with residential property, shares, and other assets all taxed at the same rates. Gains on UK residential property that already has its own 60-day reporting and payment requirement still need to be included on SA108 as well, so the figures reconcile with your overall Self Assessment position for the year.
Late filing of your Self Assessment return, including its supplementary pages, triggers the standard late filing penalties, and interest accrues on any unpaid Capital Gains Tax. If your computations rely on estimates or valuations, such as for gifted assets or unlisted shares, you flag this on the form itself, since HMRC can ask you to confirm or correct the figures once a final valuation is available.
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