What is an HMRC crypto letter?

An HMRC crypto letter is a message from HM Revenue and Customs to someone it thinks may owe tax on cryptoassets. These are usually "nudge" letters that prompt you to check your tax position, rather than the formal start of an investigation. For the underlying tax rules, see how crypto is taxed in the UK.

What are HMRC crypto nudge letters?

Nudge letters are part of how HMRC encourages people to correct their tax affairs before it opens a formal enquiry. KPMG says HMRC uses data from crypto exchanges and other intermediaries to pick recipients, and sends letters, texts and app notifications. It describes a new wave running from July 2026 to March 2027.

The volume has risen sharply. Accountancy firm UHY Hacker Young reported, citing HMRC figures, that about 65,000 letters went out in 2024 to 2025, up from about 27,700 the year before.

Are HMRC cryptocurrency warning letters linked to new reporting rules?

Yes, partly. The UK began applying the OECD's Cryptoasset Reporting Framework (CARF) on 1 January 2026, and the rules also cover UK-resident customers. GOV.UK says users must give each provider their name, date of birth, address and tax number, usually a National Insurance number or Unique Taxpayer Reference. Giving wrong details, or none, to a UK provider can bring a penalty of up to 300 pounds.

HMRC says it will start receiving this data in 2027 to help spot undeclared gains and income. KPMG puts the first report deadline at 31 May 2027.

How do you make an HMRC crypto declaration or disclosure?

For gains or income in the current or last tax year, you normally use your Self Assessment return. HMRC's August 2026 release said 2025 to 2026 gains should be declared and paid by 31 January 2027.

For older years, HMRC runs an online cryptoasset disclosure service. You need your National Insurance number, transaction and disposal counts, proceeds, costs and calculations for each year. How far back you go depends on behaviour: up to 4 years with reasonable care, 6 if careless and 20 if deliberate. Your offer usually covers tax, interest and penalties, and you should pay within 30 days. HMRC then accepts it by letter or says it cannot. Our guide to crypto losses and taxes covers losses that may reduce what is owed.

What should you do if you get an HMRC crypto letter?

Read it carefully, note any deadline, and check it really comes from HMRC before acting on it. Then compare your records with what you have declared. Exporting full exchange histories helps, as explained in how to download your crypto transaction history. KPMG notes penalties can reach 100 percent of the tax due in some cases, so many people get specialist help.

Rules differ by country and change often. Check the tax authority or a qualified professional for your own situation.