UK cryptocurrency investors are facing unexpected tax liabilities even without receiving formal warnings from HM Revenue & Customs, as the tax authority dramatically escalates its enforcement campaign against undeclared digital asset income. With 65,000 ‘nudge letters’ dispatched in the 2024-25 tax year—more than double the previous year’s total—HMRC is leveraging sophisticated data tracking methods that mean absence of correspondence provides no guarantee of compliance. Tax experts unanimously warn that enhanced international reporting agreements and exchange data sharing have created an environment where all UK crypto investors must proactively verify their tax positions.