Do you need the SA108?
- Your total gains after allowable losses were more than £3,000.
- Your total proceeds from disposals were more than £50,000, even if you made no gain.
- You want to claim a capital loss, so you can use it later.
- You sold UK residential property and already reported it on a UK property account: you still include it on the SA108.
Selling your own home is usually exempt under Private Residence Relief. Gifts to your spouse or civil partner are normally made at no gain and no loss.
The sections of the SA108
| Section | For |
|---|---|
| Residential property, carried interest and cryptoassets | Buy-to-let and second homes, carried interest, and crypto disposals (box 13.1) |
| Other property, assets and listed shares | Listed shares and funds, commercial property, land and other chargeable assets |
| Unlisted shares, losses and reliefs | Shares in private companies, loss claims and reliefs such as Business Asset Disposal Relief |
| Tax adjustments, NRCGT and other information | Adjustments, non-resident gains and box 54 for your workings |
How to complete the SA108 in Self Assessment Software
- Add capital gainsIn Income and reliefs, open CLICK TO SELECT and tick capital gains under Additional Pages this year.
- Choose each type of disposalIn the Capital Gains questions, pick the category: Listed shares, Unlisted shares, Property and other assets, Residential property and carried interest, Cryptoassets, Share scheme reliefs, or Losses.
- Enter proceeds, costs and gainsFor each category, enter the number of disposals, total proceeds, allowable costs and the gains or losses.
- Add tax already paidIf you paid Capital Gains Tax on a UK property account, enter it so it is not charged twice.
- Write your workings in box 54Explain how each gain was worked out in box 54 (Any other information).
The filing checks remind you that HMRC needs the computation behind each gain. Put it in box 54: dates, proceeds, costs, reliefs and the gain.
Rates and the annual exempt amount
| 2025-26 | Amount |
|---|---|
| Annual exempt amount | £3,000 |
| Rate within your basic rate band | 18% |
| Rate above the basic rate band | 24% |
| Business Asset Disposal Relief rate | 14% |
The software applies the annual exempt amount and works out the rate in your tax calculation. Gains use up any basic rate band left after your income.
Capital losses
You must claim a capital loss within 4 years of the end of the tax year you made it. Losses are set against gains of the same year first, then carried forward and used against future gains above the annual exempt amount.
Still stuck?
- Sold shares in lots of small trades? Total them by category, and keep the full list for your workings.
- Sold a UK home that was not your main residence? Check you reported and paid within 60 days on a UK property account.
- Capital Gains page is complete not ticked? Make sure each category has proceeds, costs and a gain or loss.
Still not sorted? Contact us and tell us the page, the tax year and any message you see.
Questions answered
What is the SA108?
The SA108 is the capital gains summary page of the Self Assessment return. You use it to report gains and losses on shares, property, crypto and other assets.
Do I need to fill in the SA108 if I made no gain?
Yes, if your total sale proceeds were more than £50,000, or you want to claim a loss.
What is the capital gains allowance for 2025-26?
The annual exempt amount is £3,000 for individuals.
Do I report crypto on the SA108?
Yes. Cryptoasset disposals have their own box in the residential property, carried interest and cryptoassets section.
What Capital Gains Tax rate do I pay?
For 2025-26, 18% on gains within your remaining basic rate band and 24% above it. Business Asset Disposal Relief gains are taxed at 14%.
Official sources
These guides explain how HMRC's rules apply in Self Assessment Software. Check GOV.UK for your own circumstances.