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HMRC crypto disclosure for unpaid cryptoasset tax.

If you have received a nudge letter about cryptoassets, or you know you have undeclared gains before HMRC's Cryptoasset Reporting Framework begins flowing exchange data from January 2027, the right move is a managed, voluntary disclosure, not silence. HMRC operates a dedicated <a href="https://www.gov.uk/guidance/tell-hmrc-about-unpaid-tax-on-cryptoassets">cryptoasset disclosure service</a> separate from the general Worldwide Disclosure Facility. Coming forward voluntarily, with a correctly reconstructed position including <a href="https://www.gov.uk/hmrc-internal-manuals/cryptoassets-manual/crypto22200">s104 pooling</a> at average cost, puts you in the best possible position on the number of years assessed and the penalty outcome. The firm handles the full process: reconstruct your transaction history, compute the correct liability, prepare and submit the disclosure, and manage HMRC correspondence through to settlement.

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4 years
Years HMRC can assess where under-declaration arose from reasonable care (non-deliberate)
6 years
Years assessable for careless under-declaration
20 years
Years assessable for deliberate concealment

The challenges clients face.

A nudge letter is not the end, but ignoring it makes it worse

HMRC's cryptoasset nudge letters are prompts, not charges. Recipients who do not respond invite an HMRC-initiated enquiry, which removes the prompt-disclosure mitigations on penalties. Responding through the dedicated <a href="https://www.gov.uk/guidance/tell-hmrc-about-unpaid-tax-on-cryptoassets">cryptoasset disclosure service</a> keeps control with you and secures the lowest available penalty band for your behaviour category.

The number of years HMRC can go back depends entirely on your behaviour

Under <a href="https://www.gov.uk/guidance/tell-hmrc-about-unpaid-tax-on-cryptoassets">HMRC's disclosure framework</a>, the assessment window is 4 years for reasonable care, 6 years for careless under-declaration, and 20 years for deliberate concealment. Getting the behaviour characterisation right at the outset matters enormously: 4 years versus 20 years of liability is a very different exposure.

Crypto-to-crypto swaps create taxable disposals even without a pound leaving your account

Every swap between tokens is a <a href="https://www.gov.uk/guidance/check-if-you-need-to-pay-tax-when-you-sell-cryptoassets">disposal at sterling market value</a> at the moment of the swap. Many holders with undeclared gains never converted to fiat; that does not reduce the liability. Reconstructing the correct exposure requires locating and valuing every swap, not only the withdrawals to a bank account.

Producing a defensible disclosure figure is skilled work, not a spreadsheet sum

<a href="https://www.gov.uk/hmrc-internal-manuals/cryptoassets-manual/crypto22200">Section 104 pooling</a> requires tracking the average cost of each token across every acquisition. Software using FIFO or specific identification produces the wrong UK figure. The same-day and <a href="https://www.gov.uk/hmrc-internal-manuals/cryptoassets-manual/crypto22250">30-day bed-and-breakfast rules</a> override the pool and are beyond any stateless tool. A disclosure built on the wrong method exposes a holder to a second enquiry.

How we help.

Full transaction reconstruction and UK-correct liability calculation

We gather exchange exports, on-chain data and any available records to rebuild your full history. Every disposal is computed under s104 pooling at average cost, with same-day and 30-day matching applied correctly. The output is a defensible liability figure, with tax, interest and a penalty-band assessment, before anything is submitted to HMRC.

Managed submission through HMRC's dedicated cryptoasset disclosure route

We prepare and submit the disclosure through <a href="https://www.gov.uk/guidance/tell-hmrc-about-unpaid-tax-on-cryptoassets">HMRC's cryptoasset-specific service</a>, with a cover narrative explaining the behaviour characterisation and the steps taken to ensure completeness. Voluntary, unprompted disclosure submitted with a correct calculation secures the lowest available penalty range for your behaviour band.

HMRC correspondence management through to settlement

We handle all HMRC responses, information requests and settlement correspondence so you are not navigating the process alone. If HMRC raises questions about the methodology or the period covered, we respond with the technical position. The engagement ends when the disclosure is accepted and the liability settled.

Common questions

I have received a nudge letter about cryptoassets. What should I do?
Do not ignore it. A nudge letter is HMRC prompting you to check your position, not a formal assessment. Responding voluntarily through <a href="https://www.gov.uk/guidance/tell-hmrc-about-unpaid-tax-on-cryptoassets">HMRC's cryptoasset disclosure service</a> secures the lowest available penalty outcome for your behaviour band and keeps the process orderly. Ignoring the letter invites an HMRC-led enquiry, which removes those mitigations.
Can HMRC actually see my exchange account?
From 1 January 2026, UK cryptoasset platforms are required to collect user and transaction data under the <a href="https://www.gov.uk/guidance/collecting-cryptoasset-user-and-transaction-data">Cryptoasset Reporting Framework (CARF)</a>. The first report to HMRC covering the 2026 calendar year is due <a href="https://www.gov.uk/guidance/reporting-cryptoasset-user-and-transaction-data">between 1 January and 31 May 2027</a>, with annual reporting thereafter. HMRC does not yet hold that data, but the collection has begun and the first report window opens in early 2027.
What is CARF and when does HMRC start getting the data?
The Cryptoasset Reporting Framework is the UK's equivalent of the Common Reporting Standard applied to crypto. UK platforms <a href="https://www.gov.uk/guidance/collecting-cryptoasset-user-and-transaction-data">collect user and transaction data from 1 January 2026</a>, covering the full 2026 calendar year. The first report to HMRC is submitted <a href="https://www.gov.uk/guidance/reporting-cryptoasset-user-and-transaction-data">between 1 January and 31 May 2027</a>, and annually by 31 May thereafter.
How many years back can HMRC assess?
Under <a href="https://www.gov.uk/guidance/tell-hmrc-about-unpaid-tax-on-cryptoassets">HMRC's cryptoasset disclosure framework</a>, the assessment window depends on behaviour: 4 years for reasonable care, 6 years for careless under-declaration, and 20 years for deliberate concealment. Getting the behaviour characterisation right at the start is one of the most important decisions in managing a disclosure.
Will I get a penalty if I come forward voluntarily?
Penalties are charged as a percentage of the tax due and vary by behaviour band (reasonable care, careless, deliberate) and by whether the disclosure is unprompted or prompted. An unprompted voluntary disclosure, made before HMRC contacts you, secures the lowest available penalty range in your band. See <a href="https://www.gov.uk/guidance/tell-hmrc-about-unpaid-tax-on-cryptoassets">HMRC's guidance</a> for the applicable penalty framework; we do not assert a fixed percentage because the ranges depend on the full facts.
I never cashed out to pounds. Do I still have undeclared tax?
Yes, you may. Every swap between tokens is a <a href="https://www.gov.uk/guidance/check-if-you-need-to-pay-tax-when-you-sell-cryptoassets">disposal at sterling market value</a> at the time of the swap, whether or not pounds ever left your exchange account. Spending crypto on goods and services and gifting crypto (except to a spouse or civil partner) are also disposals. Many holders with significant undeclared tax never made a bank withdrawal.
What is the difference between the Worldwide Disclosure Facility and the cryptoasset disclosure service?
The Worldwide Disclosure Facility is HMRC's route for offshore income and gains, typically bank accounts, investments and assets held abroad. HMRC operates a separate, dedicated <a href="https://www.gov.uk/guidance/tell-hmrc-about-unpaid-tax-on-cryptoassets">cryptoasset disclosure service</a> specifically for unpaid tax on crypto, including assets held on overseas exchanges. Most crypto disclosures route through the latter, though the specific route depends on the full facts.
I do not know my full transaction history. Can you still help?
Yes. Incomplete records are common, particularly where exchanges have closed or historical exports are unavailable. We work with whatever you have, supplement it with on-chain data where possible, and apply the methodology that HMRC expects. Where records are genuinely unavailable, the disclosure narrative explains that; a best-endeavours reconstruction on the correct method is always preferable to no disclosure at all.

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