CryptoTax UK · Guide
How to make a voluntary disclosure to HMRC for crypto tax
If you have not declared crypto gains or income from previous tax years, you are not alone — and it is not too late to put things right. HMRC actively encourages voluntary disclosure, and coming forward before they contact you can dramatically reduce any penalties you face. Educational only — not tax advice.
Calculate what I owe across all years →Why HMRC already knows about your crypto
HMRC has been receiving transaction data from UK-registered exchanges since 2019. From January 2026, the Cryptoasset Reporting Framework (CARF) requires all cryptoasset service providers to report user transaction data directly to HMRC. If you have made gains you haven't declared, the probability of detection is higher than most people assume.
The HMRC Cryptoasset Disclosure Service
HMRC has a dedicated online service for disclosing unpaid tax on crypto. You can use it to declare gains and income from any previous tax year. The service calculates the tax owed, adds interest from the original payment date, and assesses any penalty. Coming forward through this service is treated as a voluntary disclosure, which attracts the lowest penalty rates.
How penalties work: disclosure vs investigation
If you voluntarily disclose unpaid crypto tax before HMRC contacts you, penalties are typically 0–30% of the unpaid tax for careless errors. If HMRC contacts you first and then you disclose, penalties rise to 20–70%. If HMRC investigates and finds undisclosed gains themselves, penalties can reach 100–200% for offshore assets, plus interest.
How far back can HMRC go?
For innocent errors (careless), HMRC can assess the past 4 tax years. For deliberate understatement, they can go back 6 years. For cases involving offshore elements or suspected fraud, HMRC can potentially go back 20 years. The sooner you disclose, the fewer years of interest and penalty accumulate.
What you need to prepare before disclosing
Before using the disclosure service, gather: complete transaction history from all exchanges and wallets for each relevant year, a calculation of gains and income for each year (this is where CryptoTaxUK can help significantly), any previous Self Assessment returns filed, and details of any tax already paid.
Frequently asked questions
What if I genuinely can't find all my transaction records?
Do your best to reconstruct records from available sources — exchange history, bank statements, wallet explorers, email confirmations. Where records are genuinely unavailable, HMRC expects you to make reasonable estimates and document your methodology. Gaps in records are much better than not disclosing at all.
Will HMRC prosecute me if I come forward voluntarily?
Criminal prosecution for tax evasion is rare and reserved for serious deliberate fraud. Voluntary disclosure almost never results in prosecution. HMRC's stated preference is to collect unpaid tax, not to prosecute. Coming forward yourself is treated very differently from being caught.
Can I use CryptoTaxUK to prepare my disclosure figures?
Yes — CryptoTaxUK calculates your gains and losses for each tax year using HMRC's matching rules. You can use the output to prepare accurate figures for your disclosure, which reduces both the time an accountant needs to spend on your case and the risk of errors.
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Calculate what I owe across all years →Educational guidance only. CryptoTax UK is not a regulated tax adviser and the information above does not constitute tax, legal or financial advice. Always confirm your specific position with HMRC or a qualified accountant before filing.