Do You Need to Register for Self Assessment for Crypto? The 5 October Deadline
If you made crypto gains or income in 2025/26 and don't already file a tax return, you must register for Self Assessment by 5 October 2026. Who needs to, and how.
If you made money on crypto in the 2025/26 tax year and you don't already complete a tax return, there's a deadline most people miss — and it falls long before the famous 31 January date. To report crypto to HMRC you first have to be registered for Self Assessment, and the cut-off to register for 2025/26 is 5 October 2026.
Who needs to register
You need to register if, in the year to 5 April 2026, your total capital gains were above the £3,000 annual exempt amount, or your crypto income (staking, mining, earned airdrops, or being paid in crypto) was more than £1,000. You may also need to report if your total disposal proceeds for the year were more than £50,000, even if the actual gain was small. Moving coins between your own wallets doesn't count — only disposals and income do.
The 5 October 2026 deadline
If you've never filed before, you must tell HMRC by 5 October 2026 that you had taxable gains or income in 2025/26. You register online through the Government Gateway. HMRC then posts you a 10-digit Unique Taxpayer Reference (UTR), usually within about 10 working days, and you need it before you can file. Leaving registration to the last week is risky because the UTR takes time to arrive.
What you'll report
Crypto gains go on the SA108 capital gains pages, which now include a dedicated cryptoasset section. You'll need your disposals, proceeds, pooled cost basis under Section 104, and any income figures kept separately. HMRC also expects you to attach the underlying computation showing how you reached each gain.
If you miss the deadline
Registering late when tax is due can trigger a "failure to notify" penalty based on the tax you owe, on top of interest. And if late registration means you then miss the 31 January 2027 filing date, there's an automatic £100 penalty even if no tax is due.
The dates that follow
After registering, paper returns are due 31 October 2026, and online returns plus any tax owed are due 31 January 2027. Don't wait — work out whether you're over the threshold now, while you still have time to gather records. CryptoLens scans your wallets and shows your gains and income for the year in seconds.
This is general information, not personal tax advice.
Frequently asked questions
Do I need to register for Self Assessment for crypto gains?
Yes, if you're not already registered and your 2025/26 gains were over the £3,000 allowance, your crypto income was over £1,000, or your disposal proceeds topped £50,000. The deadline to register for 2025/26 is 5 October 2026.
What happens if I miss the 5 October registration deadline?
HMRC can charge a 'failure to notify' penalty based on the tax due, plus interest. If it also causes you to miss the 31 January filing deadline, there's an automatic £100 penalty even when no tax is owed.
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