The SA108 cryptoassets boxes (13.1 to 13.8), explained
Staring at the new crypto boxes on your tax return and not sure what goes where? You're in the right place. There are eight of them, 13.1 to 13.8, in the Cryptoassets section on page CG 1 of the SA108. Here's what each one means in HMRC's own words, the figure that goes in it, and a worked example, all checked against the official 2025–26 form.
If you've just spotted a row of crypto boxes on your tax return that weren't there before, don't worry, they're more straightforward than they look once you know what each one is asking for. Until recently, crypto gains went into the generic “Other property, assets and gains” section of the SA108. From the 2024–25 form onwards there's a dedicated Cryptoassets section with its own boxes, numbered 13.1 to 13.8, on page CG 1. Here's what each one means.
What each box means
| Box | HMRC's label | What goes in it |
|---|---|---|
| 13.1 | Number of disposals | How many separate crypto disposals you made in the year (a sale, a swap, a spend, or a gift each count). |
| 13.2 | Disposal proceeds | The total pound value of everything you disposed of, meaning what you got (or its market value for a swap or gift). |
| 13.3 | Allowable costs (including purchase price) | The total cost basis of those disposals, meaning the Section 104 pool cost, plus allowable fees. |
| 13.4 | Gains in the year, before losses | The total of your gains only (the disposals that made a profit), before any losses are taken off. |
| 13.5 | Losses in the year | The total of your losses only (the disposals that made a loss) in the year. |
| 13.6 | If you're making any claim or election, put the relevant code in the box | A short HMRC code only if you're making a specific claim or election (e.g. a negligible value claim). Usually left blank. |
| 13.7 | Total gains or losses … reported on Real Time Transaction returns | Only for gains you already reported in-year using HMRC's Real Time CGT service. Most people leave this blank. |
| 13.8 | Tax on gains in box 13.7 already paid | Any CGT you already paid on those Real Time-reported gains. Blank if box 13.7 is blank. |
Gains and losses go in separate boxes
Boxes 13.4 and 13.5 are separate totals. Gains and losses are not netted into one box. You report all your gains in 13.4 and all your losses in 13.5; HMRC nets them, then applies your £3,000 annual exempt amount. And HMRC asks you to enclose your computations, the working behind the figures, not just the boxes.
A worked example
12 disposals over the year
Most at a profit, a couple at a loss. The figures map straight to the boxes:
Net gain = £9,000 − £1,000 = £8,000; after the £3,000 allowance, £5,000 is taxable, at 18% and/or 24% depending on your income (see crypto tax rates). Boxes 13.6–13.8 are left blank.
How CryptoCGT helps
CryptoCGT works out exactly these figures from your transactions, using HMRC's Section 104 pooling and matching rules, and produces the computations HMRC asks you to enclose, with every number traceable back to the trade that produced it. Always check the figures against the current year's official form before you file. If you want the bigger picture of how these figures fit together, see the complete UK crypto tax guide.
Sources
- GOV.UK, Self Assessment: Capital gains summary (SA108) form and notes (Cryptoassets section, page CG 1, verified against the 2025–26 form)
- HMRC: Cryptoassets Manual
See your own number — free, no account
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Start free →This guide is information, not tax advice.Figures and thresholds are for the tax year shown (England, Wales & Northern Ireland; Scottish income tax bands differ). Rates and rules can change, and your own position may differ — check your circumstances and speak to an accountant before you file. CryptoCGT is an information tool, not a regulated tax adviser.