HM Revenue and Customs (HMRC) sent more than 81,000 warning letters, emails and texts to cryptocurrency holders in the past year, urging them to check whether they owe capital gains tax. This marks a near-tripling of such warnings since 2024, reflecting HMRC's growing focus on crypto investors, many of whom are young and may wrongly assume the tax authority cannot track their activity. Investors could face fines or prosecution if they fail to declare gains, including profits made simply by swapping one cryptocurrency for another.

Figures obtained via a Freedom of Information request by accountancy firm UHY Hacker Young show the number of warnings rose from 27,714 in 2023-24 to 81,172 in 2025-26. The crackdown comes ahead of new international powers taking effect from March 2027, which will require overseas crypto platforms to share customer data with HMRC, a move officials say could raise up to £315m by 2030. Bitcoin's price rose sharply from around £14,000 to £90,000 between December 2022 and October 2025 before falling back to roughly £48,000 today, leaving many investors with unreported gains from that period.