How to Report Crypto on Your UK Self Assessment (2025/26)

Worried you've got crypto gains to declare and no idea where they go on a tax return? Here's the reassuring part: there's no separate "crypto tax return" to hunt down. If you sold, swapped, spent or gifted crypto during the 2025/26 tax year (6 April 2025 to 5 April 2026), it goes through the normal Self Assessment system, on a supplementary page called the SA108 Capital Gains Summary. From the 2024/25 form onwards, that page has a dedicated Cryptoassets section, so HMRC now wants crypto reported in its own boxes rather than lumped in with everything else.

This guide walks through the four things that trip people up: whether you actually need to file, how and when to register, which SA108 boxes your crypto figures go in, and the records HMRC expects you to keep. It covers England, Wales and Northern Ireland. Scotland has different income tax bands, which matters for working out how much of a gain is taxed at 18% versus 24% (more on that below).

Do I need to report my crypto at all?

You need to report through Self Assessment if either of these is true for the tax year:

The second trigger catches people by surprise. Even if your gains are tiny, or you actually made a loss, you must still report if your total proceeds (the gross amount you sold or swapped, before deducting cost) cross £50,000. A handful of crypto-to-crypto swaps can add up to that quickly, because each swap counts as a disposal at its full market value.

There are two more reasons to file even when neither trigger is hit: you want to claim a capital loss so you can carry it forward to offset future gains, or you have crypto income (staking, mining, most airdrops) to declare. Crypto income is Income Tax, not CGT, and goes on a different part of your return, but it still means you need a Self Assessment account.

• Your total gains are more than £3,000. This is the 2025/26 annual exempt amount (AEA), the slice of gains everyone can make tax-free. It covers ALL your chargeable assets combined (crypto, shares, second property), not crypto alone.
• Your total disposal proceeds are more than £50,000. This is the total value of everything you disposed of, regardless of profit. This reporting trigger applies even if your gain is under £3,000 or you made a loss.

How and when do I register and file?

If you've never filed a Self Assessment return before, you have to register first to get a Unique Taxpayer Reference (UTR) and activate your online account. This can take a couple of weeks, so don't leave it to the deadline. For the 2025/26 tax year the key dates are below.

If you already file Self Assessment (for example you're self-employed), you don't need to register again. You simply add the SA108 Capital Gains Summary page to your return. Crypto does not use the "real-time" Capital Gains Tax service or the 60-day property reporting service; it goes on the annual return.

Which SA108 boxes do my crypto figures go in?

On the 2025/26 SA108 form, crypto has its own Cryptoassets section with eight boxes, 13.1 to 13.8. You add up all your crypto disposals for the year and enter the totals here. The form is explicit at the top: "You must enclose your computations, including details of each gain or loss, as well as filling in the boxes", so the boxes are summary figures, and you still attach a breakdown showing how you got there.

Here's what each box asks for. Most people only need 13.1 to 13.5; boxes 13.6 to 13.8 cover claims/elections and the rare case where tax was already paid via a Real Time Transaction return.

What records do I need to keep?

HMRC expects you to be able to show your working for every disposal. Because crypto isn't covered by the usual broker statements, the burden of keeping good records is on you. Keep these. If you only have capital gains and aren't running a business, HMRC's minimum is to keep records until at least 22 months after the end of the tax year, but for crypto you should keep acquisition records for as long as you hold the coins, because you'll need the original cost for your Section 104 pool when you eventually dispose of them (and keep everything longer if you file late or HMRC opens an enquiry):

• The type of cryptoasset and the date of every transaction (acquisitions and disposals).
• The number of units involved and the value in pounds at the time. For swaps, that's the GBP value on the day of the swap.
• Running totals for your Section 104 pool (units held and pooled cost) for each asset.
• Bank statements and wallet addresses that support the figures, plus any exchange CSV exports.
• Records of fees (you can deduct allowable transaction costs) and of any income events (staking, mining, airdrops) with their GBP value on the day received, since that value becomes the cost basis for a later disposal.

How a calculator fits in

The hard part isn't filling in eight boxes. It's working out the right figures across dozens or hundreds of transactions, matching disposals to acquisitions in HMRC's order (same-day, then the 30-day "bed and breakfast" rule, then the Section 104 pool), and keeping the pool's running average cost straight. Get the matching wrong and every box on the form is wrong.

Our free CGT calculator takes a CSV export from your exchange (or manual entries, no wallet or API connection needed) and produces the SA108 totals plus a per-disposal breakdown you can attach to your return. You can see how every figure is derived in our methodology. It does the computation; you still review it and file with HMRC.

Tax rules have edge cases. Some DeFi income, lost or worthless tokens (a negligible value claim is fact-dependent and HMRC must accept the asset is genuinely of negligible value), and complex airdrops can be genuinely uncertain. Where your situation is unusual, treat any calculator output as a starting point and consider a qualified UK tax adviser. If you want the bigger picture before you file, the complete UK crypto tax guide pulls together how rates, pooling and reporting all fit together.

Sources

• HMRC: Cryptoassets Manual (CRYPTO22000: how to calculate gains/losses)
• GOV.UK: Self Assessment Capital gains summary (SA108) form and notes
• GOV.UK: Capital Gains Tax rates and allowances
• GOV.UK: Report and pay your Capital Gains Tax
• GOV.UK: Self Assessment tax returns deadlines
• GOV.UK: Register for Self Assessment
• GOV.UK: Check if you need to pay tax when you sell cryptoassets
• GOV.UK: Domestic reporting under the Cryptoasset Reporting Framework (CARF)