HMRC nudge letter about crypto: what it means and what to do
An HMRC nudge letter is not a formal tax investigation — it's a prompt. HMRC holds data (from crypto exchanges, and increasingly from the international CARF reporting framework) suggesting you may have had crypto activity, and the letter invites you to check whether you've declared everything you should. Don't panic, and don't ignore it. The right response is to work out your actual position: if nothing is owed, keep your workings as evidence; if a recent return missed something, amend it; if older years are affected, make a voluntary disclosure — ideally with professional help, since acting before HMRC escalates keeps penalties at their lowest.
What a nudge letter actually is
HMRC sends "one to many" campaign letters when third-party data suggests a group of taxpayers may have something to declare. Crypto holders have been receiving them for several years, based on information HMRC gathers from exchanges. A nudge letter is deliberately not an enquiry: no case has been opened, nothing has been alleged, and no response deadline is set in law. It is HMRC saying, in effect, "we know you had crypto — are you sure your returns are right?"
That softness is strategic. If you correct your affairs after a nudge, HMRC collects with minimal effort. If you ignore it and they later open a real enquiry, the letter is on file showing you were warned — which affects penalties.
Why these letters are about to get more common
Until now, HMRC's crypto data came mostly from UK exchanges. Under the Cryptoasset Reporting Framework, platforms collect standardised user and transaction data from January 2026, and tax authorities exchange it internationally from 2027 — bringing overseas exchanges into view too. More data means more matching, and more matching means more letters. A nudge letter is increasingly a sign of what HMRC can see, not a guess.
The three sensible responses
- Nothing owed: work out your position properly (gains within the allowance, losses, no disposals). Keep the calculation — if HMRC ever asks, you answer in minutes
- A recent slip: you can amend a Self Assessment return within 12 months of its filing deadline — often the cleanest fix
- Older years or bigger gaps: use HMRC's disclosure routes, and consider a specialist — disclosure before HMRC escalates is treated significantly more gently than being caught after
The mistake to avoid
Ignoring it. A nudge letter costs nothing to resolve if you genuinely owe nothing — a proper calculation is your answer. But unresolved, it sits on your file while HMRC's data pile grows. The gap between "I checked and here's my working" and "I hoped it would go away" is, in penalty terms, expensive.
Start with the numbers: our free calculator applies HMRC's matching rules to your transactions and shows the full working. If the result is complicated — or the letter concerns years you never declared — that's exactly what the specialist route is for.
Run your own numbers — free
Our calculator applies these rules to your transactions and shows the full working for every disposal — same-day, 30-day and Section 104 matching, per tax year.
Open the calculator →Frequently asked questions
Is a nudge letter an investigation?
No. It's a prompt based on data HMRC holds, sent to many people at once. But it can precede one if ignored — treat it as the cheap moment to get things right.
Do I have to reply?
Some letters include a certificate or ask for a response; many just prompt you to review. Follow what the letter asks — and even where no reply is required, checking your position and keeping the working is the protection.
What if I genuinely owe nothing?
Then you're fine — many recipients owe nothing because gains sat within the allowance or losses offset them. The value of doing the calculation is being able to prove it.
Sources & methodology
- GOV.UK: Cryptoasset Reporting Framework (CARF)
- GOV.UK: Check if you need to pay tax when you sell cryptoassets
- GOV.UK: Report and pay your Capital Gains Tax
Tool v0.2.0 · sources last checked 6 July 2026. This guide is general information, not tax or financial advice — verify your position with a qualified professional before filing.