Received an HMRC Crypto Asset Nudge Letter?

HMRC's crypto nudge letters are part of its wider One to Many campaign approach, driven increasingly by data obtained directly from cryptoasset exchanges. UK exchanges can be required to provide customer and transaction data, and international information-sharing arrangements for cryptoassets are expanding the pool of overseas data HMRC can access.

A letter usually indicates that HMRC's data shows trading activity, and it invites the recipient to review whether their tax returns correctly reflect it. It does not automatically mean a mistake has been made, but it does mean HMRC already holds transaction-level information against which any reply will be checked.

Many recipients assume that only converting crypto to sterling and withdrawing to a bank account is taxable. In HMRC's view, a disposal for Capital Gains Tax purposes includes selling a token for currency, exchanging one cryptoasset for a different cryptoasset, using cryptoassets to pay for goods or services, and giving cryptoassets away other than to a spouse or civil partner.

This means an active trader who never once converted to sterling, but frequently swapped between tokens, can still have made numerous chargeable disposals across a tax year. Each swap needs to be valued in sterling at the time of the transaction and compared against the pooled acquisition cost of the tokens given up.

Whether crypto activity is taxed as capital gains or income depends on the nature of the activity, not simply the asset type. Buying and holding tokens before eventually disposing of them generally falls within Capital Gains Tax, using the normal pooling and same-day and 30-day matching rules that also apply to shares.

Mining rewards, staking rewards, airdrops received for doing something in return, and activity that amounts to a trade in its own right can instead fall within Income Tax, sometimes with a further Capital Gains Tax charge when the resulting tokens are later disposed of. Getting this classification right at the outset avoids having to unpick the calculation later.

A frequent practical difficulty is that exchange statements alone do not show the sterling value or cost basis needed for a UK tax calculation, particularly where assets moved between wallets, exchanges closed down, or transactions used a stablecoin as an intermediate step rather than sterling.

Reconstructing a multi-year, multi-exchange trading history is time-consuming but necessary; using specialist crypto tax software or a detailed manual reconciliation, and clearly documenting any assumptions used to fill genuine gaps, gives HMRC a transparent basis to review the figures.

Where the review shows undeclared gains or income, the correction route depends on the facts. A recent year still within its amendment window can sometimes simply be amended. Earlier years, or cases involving an overseas exchange or offshore element, are more often corrected through the Digital Disclosure Service or the Worldwide Disclosure Facility.

The disclosure should set out the transaction history, the calculation methodology, and the behaviour that led to the omission. Genuine misunderstanding of the token-swap disposal rules is a common and, on the right facts, a credible explanation for a careless rather than deliberate inaccuracy, but it must be supported by the actual pattern of activity, not simply asserted.

Where an exchange has closed, records were lost, or activity was spread across many wallets without a consolidated history, a full reconstruction may not be possible. In that situation, use the best available evidence, such as remaining exchange exports, blockchain explorers, bank records showing fiat transfers, and any third-party tax software exports, to produce a reasonable estimate.

Document the method and the gaps clearly in any disclosure, rather than presenting an estimate as an exact figure. HMRC is more likely to accept a transparent, well-reasoned estimate than a précis that hides the underlying uncertainty.