How to File Your Crypto Self Assessment with HMRC

London — The 2024-25 tax year brought a significant change for UK crypto investors: HMRC introduced a dedicated cryptoasset section in the self-assessment return. It sits separately from the Capital Gains Summary pages. You fill it in yourself, in sterling. And for the first time, HMRC will have a structured data field for every gain, loss and income amount you report — which means discrepancies with the exchange data that HMRC will soon receive under CARF are going to be much easier for them to spot.

If you've been putting off the crypto section of your tax return, or you've been filing but perhaps not with the rigour it deserves, here's what you actually need to do.

Do you need to file at all?

First, work out whether you're actually required to complete a self-assessment return. The triggers for crypto are:

Your total capital gains for the year exceeded the £3,000 annual exempt amount, or you made total disposals worth more than four times that amount (£12,000), even if the net gain was below the threshold. You received more than £1,000 in miscellaneous income from staking, mining, or airdrops. You received crypto through employment or as part of running a business. You already file self-assessment for other reasons (sole trader, rental income, higher-rate taxpayer) — in which case you must add your crypto to that return regardless.

If none of those apply, you likely have no filing obligation for crypto in that year. Keep records anyway.

The new cryptoasset section: what to complete

From the 2024-25 return (filed by 31 January 2026 for online submissions, 31 October 2025 for paper), the cryptoasset section asks for your total gains, total losses, and the number of disposals you made. You don't need to list every trade individually — you summarise. The working-out behind the summary, however, needs to be accurate and retained in your records.

You'll need: the total proceeds from all disposals in the year, the total allowable costs (your original purchase price plus allowable transaction fees), the net gain or loss, and any gains or losses carried forward from previous years. If you've used crypto tax software — Koinly, Recap, CoinTracker and similar tools all produce HMRC-compatible reports — export your CGT summary for the year and transfer the headline numbers across.

Declaring crypto income separately

Income from staking, mining, lending and airdrops doesn't go in the cryptoasset section — it goes in the income pages. Specifically, miscellaneous income (SA1 or the equivalent online section). The figure is the total sterling value of all tokens received as income during the tax year, valued at the market price on the day each receipt occurred. Deductible expenses (electricity for mining, gas fees where applicable) reduce this figure.

What happens if you've underpaid in previous years

HMRC published a specific voluntary disclosure facility for cryptoassets. If you've realised you haven't been reporting correctly, you can disclose unpaid tax using HMRC's online tool. The lookback period depends on your conduct: four years for careless errors made with reasonable care, six years if you were simply careless, and up to twenty years for deliberate omission. Voluntary disclosure before HMRC contacts you carries lower penalties than being caught.

Interest runs daily from the original payment due date, so delay is expensive. And it's worth knowing that HMRC regularly uses crypto exchange data, public blockchain analytics and Companies House records to identify UK residents with undeclared crypto activity.

The 31 January deadline

For online returns, the deadline for the 2024-25 tax year is 31 January 2026. Miss it and you receive an automatic £100 penalty, which escalates to £10 per day after three months, then further lump-sum penalties at six months and one year. The penalty applies regardless of whether you actually owe any tax — it's for the late filing itself.

Getting your returns in on time is straightforward if you've kept records as you go. If you've been trading actively and haven't tracked anything, the reconstruction process is the hard part. Start that now, not in January.