How to Report Crypto on Your Tax Return (SA108, 2025/26)

To report crypto on a UK tax return you fill in the Cryptoassets section of the SA108 Capital Gains Tax summary (boxes 13.1 to 13.8 on the 2025/26 form), attach a computation showing each gain or loss, and put any crypto income in box 17 of the main SA100 return. The return and any tax are due by 11:59pm on 31 January 2027. This guide goes through each box with a worked example using the same figures our calculator produces, so you can see exactly where each number comes from.

Which forms do you need to report crypto in the UK?

You need the main SA100 tax return plus, for gains and losses, the SA108 Capital Gains Tax summary. Question 7 on the 2025/26 SA100 asks whether you need to fill in the Capital Gains Tax summary and provide computations, with a tick-box to confirm the computations are provided. Crypto income, if you have any, goes on the SA100 itself rather than the SA108.

Crypto disposals have had their own section on the SA108 since the 2024/25 return. Before that, they went in the "Other property, assets and gains" section (boxes 14 to 22 on the same form). For 2025/26 the Cryptoassets section sits between the residential property boxes and the "Other property, assets and gains" boxes, and is numbered 13.1 to 13.8.

Do you have to fill in the SA108 for crypto?

HMRC's SA108 notes say to fill in the Capital Gains Tax summary if any of these apply:

• you sold or disposed of chargeable assets worth more than £50,000 in total
• your chargeable gains before taking off losses were more than the £3,000 annual exempt amount
• you want to claim an allowable capital loss, or make a claim or election for the year

The £50,000 test is about the value of the assets you disposed of across all chargeable assets, not just crypto, and not about your profit. So someone who sold £60,000 of bitcoin at a small loss still needs the summary, while someone with a £2,000 gain on £10,000 of proceeds and no other disposals may not. Our guide to when you pay tax on crypto explains what counts as a disposal.

If you are not in Self Assessment and only have a capital gain to report, you can use HMRC's real time Capital Gains Tax service instead of a full return; see crypto tax deadlines for the dates.

What do you put in each Cryptoassets box on the SA108?

The Cryptoassets section asks for the year's totals, not each trade. HMRC's notes for boxes 13.1 to 13.5 are short, and the table shows them beside a worked example.

The example. This is the 2025/26 half of the two-year bitcoin example in our Capital Gains Tax guide: a same-day, 30-day and pool sale on 10 June 2025 and a swap of 0.3 BTC for ETH on 1 August 2025, with £20,000 of taxable income. The figures are exactly what the calculator's engine produces.

The two disposals are the 10 June sale (proceeds £45,000, allowable cost £31,500, gain £13,500) and the 1 August swap (proceeds £27,000, allowable cost £10,500, gain £16,500). The proceeds add up to £72,000, the costs to £42,000 and the gains to £30,000.

Three details cause most mistakes:

• Box 13.1 counts disposals, not transactions. HMRC treats all disposals of the same token on the same day as one disposal, so the calculator reports one disposal per asset per UK day. See our methodology for how we count.
• Boxes 13.4 and 13.5 are gross of each other. Gains go in 13.4 and losses in 13.5 separately; you do not enter the net figure. The Capital Gains Tax calculation applies losses and the allowance afterwards.
• A crypto-to-crypto swap is a disposal. The 1 August swap counts as one disposal with proceeds equal to the sterling value of the ETH received, even though no pounds arrived. Our section 104 pool guide shows how the pool cost was worked out.

Where do losses brought forward and carried forward go?

Losses brought forward go in box 45 in the "Losses and adjustments" section, and unused losses to carry forward go in box 47. HMRC's notes say you can use losses brought forward only to reduce your gains to the annual exempt amount (£3,000 for 2025/26), so only put in box 45 what you can actually use this year.

For example, with gains of £10,000 and £8,000 of losses brought forward, you use £7,000 to bring the gain down to £3,000, which the annual exempt amount then covers, and carry £1,000 forward in box 47. Our guide to crypto losses explains how to claim a loss in the first place and the four-year time limit.

How much tax is due, and is it entered on the SA108?

You do not enter the tax on the SA108. HMRC works out the Capital Gains Tax from the summary boxes and your other income when you submit. In the example above, gains of £30,000 less the £3,000 allowance leave £27,000 taxable. With £20,000 of taxable income there is £17,700 of basic rate band left, so £17,700 is taxed at 18% (£3,186) and £9,300 at 24% (£2,232): a total of £5,418.

It is worth working this out yourself first, because the return calculation is only as good as your boxes. Our Capital Gains Tax guide explains the rates and the calculation in full.

Do you have to attach your crypto computation?

Yes. HMRC's notes say you must send your computations, including details of each gain or loss, as well as filling in the boxes, and that you should not write "see attached" instead of completing a box. Your exchange's transaction report is not a computation, because it does not track pooled costs.

A computation HMRC can review shows, for every disposal:

• the date, the asset and the quantity disposed of
• the sterling proceeds
• the cost matched to it, and which rule matched it (same-day, 30-day or section 104 pool)
• the gain or loss

It should also include the pool before and after each disposal. That is what our paid report produces; you can see an example in the sample report. Whatever tool you use, keep the underlying records too: HMRC's manual (CRYPTO10400) expects the type of token, the date, whether it was bought or sold, the number of units, the sterling value, the running total held, and your bank statements and wallet addresses.

Where does crypto income go on the return?

Crypto income from staking, mining, lending interest or rewards does not go on the SA108. Where it is not a trade, HMRC's manual (CRYPTO21200) treats the sterling value of what you receive as miscellaneous income. HMRC's Self Assessment notes say miscellaneous income above the £1,000 allowance goes in box 17 ("Other taxable income") of the main SA100, with a description in box 21. If you have claimed the £1,000 trading allowance against it, make a note of the amount claimed in box 21.

If your activity is organised enough to count as a trade, it goes on the self-employment pages instead. Our staking, mining and airdrops guide explains where that line sits and how each reward is valued.

What if you used the real time Capital Gains Tax service?

If you reported crypto disposals through HMRC's real time service, put the overall gain or loss in box 13.7 and the tax you paid in box 13.8. HMRC's notes say those individual gains and losses must also be included in the box 13.4 and 13.5 totals, and that you should put the reference numbers of the real time submissions in box 54.

What if you have estimates or missing records?

Put an X in box 53 if your computations include any estimates or valuations, and explain in box 54, or in the computation itself, where and why you used an estimate and how you worked it out. HMRC does not accept estimates as a substitute for looking for the records: exchanges keep data for a limited time, so download every export you can before you rely on an estimate. Our exchange guides show how to export your history from Coinbase, Kraken, Binance, Crypto.com or Revolut.

If your history starts part-way through, the calculator lets you add an opening balance with the quantity, total cost and date you can support, and flags negative balances so you can see where history is missing. Do not invent a figure.

When is the deadline, and what about earlier years?

For 2025/26, the online return and any tax are due by 11:59pm on 31 January 2027. If you have never sent a return and needed to, GOV.UK says you had to tell HMRC by 5 October 2026; registering after that risks a penalty. Our crypto tax deadlines guide lists every date, including the real time service and penalties.

If you left crypto off a return from an earlier year, the fix depends on how long ago it was. A 2024/25 online return can usually be amended until 31 January 2027; older years are for HMRC's Cryptoasset Disclosure Service. See our disclosure guide, and if HMRC has written to you, use the HMRC letter helper.

Sources

• SA108 Capital Gains summary, tax year 2025 to 2026 — GOV.UK
• Capital Gains Tax summary notes 2025 to 2026 (SA108 notes) — HMRC
• Tax return SA100 2025 to 2026 — HMRC
• Tax return guide SA150 2025 to 2026 — HMRC
• Check if you need to pay tax when you sell cryptoassets — GOV.UK
• Self Assessment tax returns: deadlines — GOV.UK
• CRYPTO10400 — Record keeping — HMRC Cryptoassets Manual
• CRYPTO21200 — Staking — HMRC Cryptoassets Manual