The UK tax authority sharply increased its scrutiny of cryptocurrency investors during the 2025-26 financial year, sending 81,172 warning letters, emails and text messages over possible unpaid tax.
The figure nearly triples the 27,714 messages sent during 2023-24, highlighting a major expansion in HM Revenue and Customs’ crypto compliance efforts. The latest figures came from a Freedom of Information request obtained by accountancy firm UHY Hacker Young and reported this week.
HMRC Targets Undeclared Crypto Gains
HMRC has warned that investors can face tax obligations when they sell cryptocurrency for a profit. Tax can also arise when investors exchange one cryptocurrency for another or use digital assets to purchase goods and services.
The warnings do not necessarily mean recipients owe tax. Instead, they indicate that HMRC has identified activity that could point to undeclared income or capital gains.
The increase comes after a strong crypto market rally. Bitcoin climbed from roughly £14,000 in December 2022 to around £90,000 by October 2025. HMRC believes some gains from that period may remain unreported.
The tax authority’s growing focus has prompted accountants to urge crypto investors to review their records and reporting history.
International Data Sharing Adds Pressure
HMRC is also preparing for broader access to cryptocurrency transaction information. From March 2027, crypto platforms in dozens of countries outside the UK are expected to share customer information with tax authorities under new international reporting arrangements.
HMRC estimates those changes could generate as much as £315 million in additional tax revenue by April 2030.
For UK investors, the message is increasingly clear: cryptocurrency activity is becoming harder to keep outside the tax system. As authorities gain access to more exchange and transaction data, investors with previously undeclared gains may face greater scrutiny.
