The SA108 form is a supplementary page which sometimes needs to be submitted alongside the paper-based Self Assessment tax return by people reporting capital gains.
Do I need to submit an SA108 form?
If you submit your main Self Assessment tax return using the paper based SA100 form and you need to tell HMRC about any capital gains or losses which you made during the tax year, you may need to include an SA108 form with your return.
Capital gains are the profits you make when you ‘dispose’ of an asset. This usually means that you’ve sold it, but disposing of an asset can also mean that you’ve gifted it to someone else, swapped it, or been compensated for it another way.
You’ll need to pay Capital Gains Tax if the total ‘gain’ you make in a year is more than Annual Exempt Amount – a tax-free allowance for capital gains. The annual thresholds are shown in the table below.
| 2025/26 | 2026/27 | |
| Individuals | £3,000 | £3,000 |
| Trustees | £1,500 | £1,500 |
Should I complete an SA108 if I do my Self Assessment online?
No, you’ll only need to complete and submit the SA108 form to report Capital Gains Tax if you use the paper-based version of the Self Assessment return. When you complete your tax return online, you’ll be asked a series of questions to tailor your return so that it includes all of the sections that you need.
How do I submit an SA108 form?
You’ll need to download the SA108 form from the HMRC website – make sure you use the correct form for the tax year that you’re reporting!
Once it’s complete, submit it along with your main tax return form and any other supplementary pages to the address shown on the main form.
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