How to report crypto on UK Self Assessment (step-by-step 2026)

Filing crypto on UK Self Assessment is a six-step job, most of which is just clicking through the right pages on HMRC online and pasting the right four numbers. The work happens before you log in — getting your computation right. This guide covers both the prep and the submission, with the exact boxes that take crypto figures.

Before you start

Have ready:

• Your Government Gateway login. If you don't have one, request it from gov.uk Self Assessment online. Setup involves an activation code by post, so allow 10 working days.
• Your UTR. The 10-digit Unique Taxpayer Reference, on every HMRC letter.
• Your computation. Four totals from your tax software for SA108: number of disposals, total proceeds, total allowable costs, gains before losses. Plus a separate income figure for SA100.
• The PDF report. The full transaction-level workings to attach as supporting evidence.

If you have not generated the computation yet, see how to calculate UK crypto taxes and our software roundup.

Step 1 — log in

Visit gov.uk and sign in to the Self Assessment service. From the dashboard, select the relevant tax year (for the 2025/26 return, that is the year ending 5 April 2026, filing window opening 6 April 2026). Click "Start" or "Continue" on the return.

Step 2 — tailor the return

The first substantive page is "Tailor your return". This is a series of yes/no questions that turn on the supplementary pages you need. The relevant questions for crypto are:

• "Did you dispose of any chargeable assets?" Tick yes if your gains exceed £3,000, your proceeds exceed £50,000, or you want to claim a loss. This unlocks SA108.
• "Did you receive any other UK income?" Tick yes if you had any staking, mining, lending or earned-airdrop income. This unlocks the relevant section of SA100.

Step 3 — staking and income

On the "Other UK income" page (page TR3 of the paper SA100), look for box 17 — "Other taxable income" with a free-text description. Enter the £ amount your tax software flagged as crypto income, and a short description such as "Cryptoasset staking and lending rewards".

This figure is taxed at your marginal income tax rate (20% / 40% / 45%) and folded into the income tax calculation. It does not belong on SA108.

Step 4 — SA108 boxes

The Capital Gains Summary appears as its own section. The online interface walks you through the questions in narrative order; the underlying boxes are the same 14-22 from the paper SA108. Enter:

The system computes net gain, applies the £3,000 annual exempt amount, and works out the CGT due at 18% / 24% based on your income band. You can preview the calculation before submitting.

Step 5 — attach the computation

On the "Attachments" or "Supporting documents" page, upload the transaction-level PDF from your tax software. This is not formally required, but it is strongly recommended:

• It demonstrates a methodical calculation, which discourages enquiry.
• If HMRC does enquire, the figures are already on file, halving the back-and-forth.
• It documents the matching method (HMRC ordering rules) for future reference.

Koinly, Coinpanda and CoinLedger all generate a single PDF suitable for upload.

Step 6 — submit and pay

Review the full return summary. Confirm the total tax due (income tax + CGT − payments on account). Submit. You receive an immediate confirmation reference.

Pay the tax owed by 31 January following the tax year (same date as the filing deadline). Faster Payments, debit card and direct debit are all supported. Payment after the deadline accrues interest and a 5% surcharge after 30 days.

Edge cases — what to do when

You can't reconcile a transaction.Estimate on a reasonable, documented basis — for example, the fair market £ value at the closest available timestamp. Add a note in the "any other information" box explaining the assumption. HMRC accepts reasonable best-effort estimates when they are clearly flagged.

You realise a mistake after submission. Self Assessment can be amended online for up to 12 months after the original deadline. After that, write to HMRC with the correction.

You owe more than £30,000 and can't pay. Use the HMRC online Time to Pay arrangement. Filing is still required by the deadline; the arrangement only spreads the payment.

You discover unfiled crypto from a previous year. Use the Voluntary Disclosure Facility — penalties are typically lower for proactive disclosure than for HMRC discovery.

For situations where DIY is not enough, see do you need a crypto tax accountant?. To check whether you qualify for any reportable losses, see claiming UK crypto losses.