HMRC sent 65,000 warning letters in 2025 to crypto holders; hmrc crypto letters aim to nudge investors to declare undeclared gains.
HMRC combines mandated exchange data sharing with blockchain analysis to trace flows between wallets and reduce pseudonymity.
Exchanges provide identity-linked records and transaction histories, while analytics map movements that suggest undeclared profits. Together these tools allow faster linkage of on-chain activity to real-world accounts, shortening investigative timelines.
The agency said it sent 65,000 letters in 2025, targeting individuals it believes may have undeclared gains within an estimated pool of 7 million Britons owning digital assets.
Letters ask recipients to clarify past trades and balances and warn that failure to disclose taxable events can trigger further enquiries. HMRC says the outreach is intended to improve voluntary compliance rather than imply automatic guilt.
Those who do not respond or who are found to have undeclared gains may face penalties, interest and, in cases of deliberate evasion, possible criminal investigation.
Penalty levels depend on the size of unpaid tax and the taxpayer’s conduct; specifics should be checked against HMRC guidance or legal advice.
Privacy groups warn that wider use of data-sharing and blockchain tracing tools can erode user anonymity and raise proportionality and data-protection questions.
In brief, HMRC’s 2025 letter campaign uses exchange data sharing and blockchain analysis to pursue undeclared gains among a subset of Britain’s crypto holders; the move tightens enforcement but raises privacy concerns.
If you receive a letter, preserve transaction records, download exchange statements and seek professional tax advice promptly.
Industry reports note rapid improvements in on-chain tracing capabilities.
For example, a market analysis by Chainalysis describes how analytics firms support investigations into suspicious flows. HMRC also states it will use available data to improve compliance efforts and close tax gaps (HMRC).
Technical vendor names and exact penalty calculations vary by case and should be confirmed with primary sources.
The number 65,000 letters and the year 2025 have been verified by HMRC.
Internal context: see related analysis on blockchain privacy and traceability on Cryptonomist for background.
