SA108 Crypto 2025/26: Boxes 13.1-13.8 Explained

HMRC's 2025/26 SA108 keeps a dedicated section for crypto assets and digital tokens. It uses boxes 13.1 to 13.8 for disposals made between 6 April 2025 and 5 April 2026. The online filing and payment deadline is 31 January 2027.

The boxes look simple, but they are totals produced by a larger calculation. You still need to identify disposals, convert each transaction to pounds sterling, apply same-day and 30-day matching, maintain Section 104 pools, and retain a computation that reconciles to the return.

Do you need to complete SA108?

The 2025/26 SA108 notes say the Capital Gains pages are required in several circumstances. Common triggers include disposing of chargeable assets worth more than £50,000 in total, or having gains before losses above the £3,000 annual exempt amount. You may also need the pages to report a loss, claim a relief, or make an election.

Those tests cover all chargeable assets, not crypto in isolation, and Self Assessment registration depends on your wider circumstances. See our 2025/26 crypto Self Assessment guide for the wider filing decision and deadlines.

What counts as a crypto disposal?

HMRC lists selling tokens for money, exchanging one token for another, spending tokens, and most gifts as disposals. A transfer between wallets you beneficially control is normally not a disposal. DeFi transactions can be more fact-dependent because the tax result turns on what rights and beneficial ownership changed.

Do not use the number of exchange CSV rows as box 13.1. Purchases, income receipts, and genuine self-transfers are not disposal entries. HMRC's same-day rule can also treat multiple disposals of the same token on the same day as a single disposal for the calculation.

SA108 crypto boxes 13.1 to 13.8

Box 13.1: number of disposals

Enter the number of crypto disposals made in your personal capacity during the year. Exclude acquisitions, income-only receipts, and movements where you retained beneficial ownership throughout. The count should agree with your supporting computation after the tax matching rules have been applied.

Box 13.2: disposal proceeds

Enter total disposal proceeds in pounds sterling before deducting costs or applying claims and reliefs. A crypto-to-crypto exchange has no cash proceeds, but it can still have sterling disposal value based on market value at the transaction time.

Box 13.3: allowable costs

Enter total allowable costs, including the relevant acquisition cost. For pooled tokens this is not necessarily the cost shown next to the asset in one exchange export. Same-day matching, the 30-day rule, and the Section 104 pool determine which cost is matched to each disposal. Eligible transaction fees can also form part of allowable costs, subject to the normal CGT rules.

Box 13.4: gains in the year, before losses

Add the positive gains from the year after any applicable deductions or reliefs, but before offsetting losses. Do not enter the final net gain. Gains included in box 13.7 must also be included here.

Box 13.5: losses in the year

Add the losses arising in 2025/26 and enter the total as a positive amount. Do not mix in unused losses brought forward from earlier tax years. Losses included in box 13.7 must also be included here. Our crypto capital losses guide explains loss claims and carry-forward separately.

Box 13.6: claim or election code

Enter the code from the claims and elections table in the current SA108 notes if one applies, and explain the claim in your computation. Leave the box blank when no listed claim or election applies. This box is not the arithmetic difference between boxes 13.4 and 13.5.

Boxes 13.7 and 13.8: real-time service

Use box 13.7 for the overall gain or loss on crypto disposals already reported through HMRC's real-time Capital Gains Tax service. The underlying positive gains and losses still need to appear in boxes 13.4 and 13.5. Put tax already paid through that service in box 13.8, and include the real-time submission references in box 54.

If you did not use the real-time service for crypto during 2025/26, these boxes will normally be zero or blank as the form or filing software directs.

Worked example

Suppose your final computation contains four disposals with total proceeds of £28,000 and allowable costs of £22,300. Two disposals produced gains totalling £6,200 and two produced losses totalling £500. You made no claim or election and used no real-time service.

The £5,700 net result is useful in the wider tax calculation, but it does not go in box 13.6. Any annual exempt amount, brought-forward losses, and CGT rate calculation are dealt with in the later parts of the return and computation.

Your computation still matters

HMRC's notes tell you to send computations for each gain or loss and to complete the relevant boxes rather than entering only "see attached". A reviewable crypto computation should show the disposal date, asset and quantity, sterling proceeds, matched allowable cost, gain or loss, and how the matching rules were applied.

• Tick box 53 if your computation contains estimates or valuations.
• Use box 54 for relevant additional information and real-time service references.
• Keep source records, exchange exports, wallet addresses, and valuation evidence.
• Reconcile boxes 13.1 to 13.5 to the detailed computation before filing.

Box 51 is different in 2025/26

The 2024/25 return needed a special adjustment because the main CGT rates changed part-way through that tax year. Do not carry that split-year treatment into 2025/26. Box 51 on the current form is for specified tax adjustments, not a routine crypto total. Use it only if one of the adjustments described in the 2025/26 SA108 notes applies.

If you are completing the earlier return, use the historical 2024/25 SA108 guide instead.

Crypto income goes elsewhere

The SA108 crypto section is for capital disposals. Staking rewards, mining receipts, lending returns, and some airdrops may be taxable as income depending on the facts. A later disposal of those tokens can then create a separate capital gain or loss. See our staking rewards and HMRC guide.

Prepare reviewable 2025/26 working

ChainTax brings supported exchange and wallet activity into one UK calculation, applies same-day, 30-day, and Section 104 matching, and produces reviewable working behind the SA108 totals. Unresolved or uncertain classifications remain visible for review rather than being presented as settled tax conclusions.

Official sources

• HMRC: Capital Gains Tax summary (SA108)
• HMRC: SA108 2025/26 form (PDF)
• HMRC: SA108 2025/26 notes (PDF)
• HMRC: tax when disposing of cryptoassets
• HMRC: Self Assessment deadlines