Offshore Crypto Tax Exposure Under HMRC Scrutiny

What Makes a Cryptoasset Holding “Offshore” for UK Tax Purposes?

Offshore crypto tax exposure starts with a definition problem. In HMRC’s eyes a holding of crypto by a UK resident is never really “offshore” even if it is held overseas for example, on Binance or Kraken, or kept in a cold wallet that is physically abroad. This is because HMRC regard the crypto as situated wherever the true owner is tax resident so that crypto owned by a UK tax resident is treated as situated in the UK. Crypto is only “offshore” if it is owned by a non-UK tax resident and kept offshore.

Why Offshore Cryptoassets Are Increasingly Visible to HMRC

It is increasingly likely that HMRC will already have details of your crypto transactions. Under The Reporting Cryptoasset Service Providers (Due Diligence and Reporting Requirements) Regulations 2025 HMRC receive information about crypto transactions from UK exchanges.

These regulations apply the rules and commentary set out in the OECD Crypto-Asset Reporting Framework, (“CARF”) and require platforms with a UK connection that carry out exchanges between crypto and fiat currencies or between different crypto assets to carry out due diligence on users and let users know that information about their crypto transactions will be reported to HMRC. This type of data collection began on 1 January 2026 and the data must be supplied to HMRC by May 2027.

Information about users who are not UK resident is also collected and HMRC sends that information to the tax authorities in other countries that have a CARF. HMRC also receives information from other countries about potential tax evasion and avoidance by persons connected with the UK who carry out crypto transactions. This gives HMRC knowledge of crypto transactions carried out on the main crypto exchanges in order to cut down on tax evasion and avoidance through non-reporting of crypto gains. It’s safer to assume that HMRC know about your crypto transactions and act accordingly.

When Offshore Crypto Activity Creates a UK Tax Liability

HMRC normally treat offshore crypto gains arising to a UK tax resident from either sales of crypto for fiat currency or exchanges of one form of crypto for another as a capital gain liable to CGT. However, income tax will apply where you are paid in offshore crypto for services instead of cash or you receive interest on DeFi lending or from staking.

Undeclared Offshore Crypto and HMRC Discovery Assessments

HMRC have up to 20 years to claw back the tax you should have paid if HMRC can show that you knew or must have known that tax was due and yet you deliberately failed to declare it; 12 years for certain matters involving offshore gains – see further below; 6 years if you have been careless in not reporting the gain and 4 years if they simply “discover’ your unreported gain after the normal 12 month enquiry period into your tax return has expired even if you have not been careless.

Extended Assessment Time Limits for Offshore Matters

In offshore matters, HMRC has a blanket 12-year time limit to assess undeclared income tax, CGT and Inheritance Tax. This applies to non-deliberate errors or a failure to take reasonable care and replaces the usual 4-year or 6-year “discovery” limits that apply to onshore matters. Tax fraud or dishonest behaviour extends the clawback period to 20 years.

Penalties for Undeclared Offshore Cryptoassets

Serious penalties can apply if you fail to declare crypto gains to HMRC up to and including criminal prosecution and seizure of your crypto in the worst cases. You can face late filing penalties if you do not file your tax return on time, a £300 penalty if you fail to supply your correct personal details to a regulated crypto exchange, penalties for careless behaviour of 0% to 30% of the tax and then 20% to 100% of the tax (or up to 200% if there is an offshore dimension) if your failure has been deliberate, plus interest on the unpaid tax.

If you have undeclared crypto tax liabilities, HMRC will allow a significant reduction in potential penalties for approaching them to make a voluntary disclosure prior to you being prompted to do so. You could achieve a reduction to 0% for a careless inaccuracy, 20% for a deliberate inaccuracy and 30% for a deliberate and concealed inaccuracy in relation to onshore matters. For offshore matters the minimum penalties for voluntary disclosures are higher but still significant.

Reasonable Excuse and Crypto Tax Compliance

Whether the taxpayer has a “reasonable excuse” for not reporting offshore crypto gains will depend on all the surrounding circumstances and there is no specific tax definition of “reasonable excuse”. At CH160200 HMRC state that:

“When considering this you must look at what a reasonable person with the same attributes and abilities who wanted to comply with their tax obligations would have done in the same circumstances and determine if the actions of the person met that standard.

If there is a reasonable excuse it must exist throughout the period of default.”

In other words, HMRC will look at the attributes of the taxpayer concerned such as age, experience, health, education etc but view these through the eyes of a reasonable person in the position of the taxpayer and what that person would have done.

An issue with crypto tax avoidance however will be that the taxpayer investing in and using crypto will normally be expected to have a certain degree of intelligence, mental acuity, financial knowledge and sophistication and this will normally make it much harder to run a reasonable excuse argument for failing to report and pay tax on crypto transactions.

Making a Voluntary Disclosure Before HMRC Opens an Investigation

The reduction in penalties for making an unprompted disclosure can be significant even with offshore crypto, as noted above. According to HMRC at CH403202:

“A disclosure is unprompted if it is made at a time when the person making it has no reason to believe that HMRC have discovered or are about to discover the inaccuracy, under-assessment, failure to notify, deliberate withholding of information or wrongdoing. Otherwise, it is prompted.

Disclosures made during a compliance check will usually, but not always, be prompted. A disclosure could be considered unprompted if the inaccuracy, under-assessment, failure or wrongdoing disclosed was outside the scope of the compliance check and would not have been found in the normal course of the check.”

When an HMRC Crypto Enquiry Becomes a Tax Dispute

When HMRC are carrying out a check into crypto and challenges over valuation, the source of funds, beneficial ownership, tax residence, transaction reconstruction, tax characterisation and taxpayer behaviour arise then the check risks turning into a tax dispute and can end with either a closure notice or a discovery assessment being issued requiring the disputed tax to be paid. At that point the taxpayer must decide whether to concede or issue a notice of appeal against HMRC.

When to Instruct a Tax Barrister

If HMRC’s check will potentially require complex disclosures of past crypto activity, significant historic liabilities, disputed assessments, potential penalties and issues of tax residence then you should give serious consideration to instructing a barrister with specialist knowledge and experience of advising and assisting crypto clients under tax investigation by HMRC. We have extensive experience in advising and representing clients under HMRC investigation with historic crypto tax liabilities and will try to achieve the best possible outcome should you find yourself either under HMRC investigation or could potentially have crypto tax liabilities that need to be reviewed. Contact Cannon Chambers here.