SA108 is the Capital Gains Tax summary that goes with your Self Assessment tax return. For the 2025 to 2026 tax year you must fill it in if, for example, you disposed of chargeable assets worth more than £50,000, or your gains before losses were more than the £3,000 annual exempt amount. You also need it to claim a capital loss or make a capital gains claim or election.
Everything below comes from HMRC's SA108 2026 form and notes for the tax year 6 April 2025 to 5 April 2026, plus the GOV.UK Capital Gains Tax guide, as of October 2026.
When the SA108 pages are compulsory
- You sold or disposed of chargeable assets worth more than £50,000.
- Your chargeable gains before taking off losses were more than £3,000, the annual exempt amount.
- You have gains from an earlier year that are taxable in this one.
- You want to claim an allowable capital loss, or make a capital gains claim or election.
- You previously used the remittance basis and have remitted foreign gains from an earlier year.
- You're claiming under the new foreign income and gains (FIG) regime or the temporary repatriation facility.
- You made a direct or indirect disposal of UK property or land while non-resident, or in the overseas part of a split year.
Disposals you can leave off
| You don't need SA108 if you only disposed of | Why |
|---|---|
| Private cars | Exempt from Capital Gains Tax |
| Personal possessions worth up to £6,000 each, such as jewellery or paintings | Chattels below that value are exempt |
| Shares held in ISAs or PEPs | Tax-free wrappers |
| UK gilts, Premium Bonds or National Savings Certificates | Exempt government securities |
| Your main home, where Private Residence Relief covers the whole gain | Relief removes the gain |
That second test is the one people forget. Even if your gains are under £3,000, you'll still need SA108 when the total value of what you disposed of was more than £50,000. It's a reporting test, not a tax test, so you can owe nothing and still have to file the pages.
The 60-day rule for UK homes
If you sold or disposed of an interest in UK residential property and owe Capital Gains Tax, you must tell HMRC within 60 days of completion, through the Capital Gains Tax on UK property service. That's separate from your tax return. On SA108, you put the overall gain or loss from those property returns in box 9, and the tax you already paid in box 12, so it isn't charged twice.
Losses to family and other connected people
If you sell, give or receive an asset to or from a connected person, you may need to use the market value instead of the price paid when you work out the gain or loss. And if that disposal makes a loss, you can only use it against gains on other disposals to the same connected person. HMRC calls this a clogged loss, and you'll need to keep a separate record of each one you carry forward. It's one reason a sale to a relative at a low price doesn't save the tax you'd expect.
Cryptoassets have their own boxes
Disposals of cryptoassets go in boxes 13.1 to 13.8. Box 13.1 is the number of disposals, and box 13.2 is the total disposal proceeds before costs. Ignore disposals you made in another capacity, such as a trustee. If you used HMRC's real time Capital Gains Tax service during the year, enter the reference numbers of those submissions in box 54.
Current rates and the allowance
GOV.UK sets the tax-free allowance at £3,000, or £1,500 for trusts. It gives the rate as 18% on gains that fall within your basic rate band and 24% on anything above it, the rates it publishes for gains from 6 April 2026, with 18% for gains that qualify for Business Asset Disposal Relief from that date. You add your taxable gains to your taxable income to see which band they land in.
GOV.UK's own example: taxable income of £20,000 and taxable gains of £12,600. Take off the £3,000 allowance, leaving £9,600. Added to income that makes £29,600, which is under the £37,700 basic rate band, so the gain is taxed at 18%, which is £1,728. These figures are as of October 2026.
Filling in SA108, step by step
- Work out each gain or loss, with a separate computation for each disposal, and keep it.
- Fill in the summary boxes for each type: UK residential property and carried interest, other property, assets and gains, listed shares, unlisted shares, and cryptoassets.
- Add any losses brought forward and claims, such as Business Asset Disposal Relief.
- Put box 9 and box 12 figures from any 60-day property returns.
- Attach your computations, then complete the main SA100 return.
New UK residents and the FIG regime
If it's one of your first 4 years of UK residence after at least 10 consecutive tax years of non-UK residence, you're a qualifying new resident. You claim relief for foreign gains under the FIG regime on the SA109 residence pages, using box 29, and then use SA108 for the gains themselves.
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The verdict
SA108 isn't only for people with big gains. Check both tests, value over £50,000 and gains over £3,000, report any UK home sale within 60 days separately, and count every crypto swap. If you've got a loss, file SA108 anyway: claiming it now is what lets you set it against future gains. The return itself is due by the usual Self Assessment deadline.
Frequently asked questions
Do I need to fill in SA108?
For 2025 to 2026, yes if you disposed of chargeable assets worth more than £50,000, your gains before losses were more than £3,000, or you want to claim a loss or make a claim or election, among other reasons.
Do I need SA108 if my gains are under £3,000?
You may still need it if the assets you disposed of were worth more than £50,000, or if you want to claim a capital loss.
What can I leave off SA108?
Private cars, personal possessions worth up to £6,000 each, ISA and PEP investments, UK gilts and similar government securities, and your main home if Private Residence Relief covers the full gain.
Where does tax from a 60-day property return go on SA108?
Put the overall gain or loss from those returns in box 9 and the tax you already paid in box 12.
What is the Capital Gains Tax allowance?
GOV.UK gives the tax-free allowance as £3,000, or £1,500 for trusts.
