According to Protos, the UK’s HM Revenue and Customs (HMRC) sent more than 81,000 warning letters to crypto holders suspected of unpaid taxes during the 2025/26 financial year, nearly triple the 27,714 letters sent in 2024.

HMRC said the unpaid taxes largely stem from gains made during the crypto bull market between 2022 and 2025. Selling, gifting, swapping or using crypto for purchases may trigger capital gains tax obligations, while unpaid taxes can result in penalties of up to 100% of the amount owed, plus interest. HMRC expects new powers next year to require offshore crypto firms to disclose customer information and estimates the measures could raise £315 million by 2030.