HMRC Sent 81,000 Crypto Warning Letters in 2025/26

HMRC tripled its crypto enforcement outreach in a single year, sending more than 81,000 warning letters to UK crypto holders during the 2025/26 financial year. If you received one, or you're worried you might, this is what it means and what you should do next. The volume is a direct signal that the agency is scaling up its use of data to identify people who may not have properly reported gains or income from crypto, and the stakes are high: penalties can reach 100% of the unpaid tax, plus interest.

What the Numbers Actually Show

A Freedom of Information request, reported by the BBC, revealed that HMRC dispatched over 81,000 nudge letters to suspected crypto non-filers in 2025/26. That compares to 27,714 letters in the previous year, meaning the volume has roughly tripled in twelve months.

Why the spike in 2025/26?

HMRC has said it believes the bulk of the unpaid liability relates to gains made during the crypto bull run that ran from 2022 into 2025. If you bought bitcoin, ether, or any other cryptoasset during that period and sold, swapped, or otherwise disposed of it at a profit, a capital gains tax event most likely arose. Many holders either didn't know this or assumed HMRC lacked the data to find out. That assumption is becoming harder to sustain.

Neela Chauhan, a partner at accounting firm UHY Hacker Young, told the BBC that many crypto investors are young, have had little prior contact with HMRC, and work under the belief that the tax authority has limited visibility into their activity. She described the tracking of wealthier crypto users as potentially "shooting fish in a barrel" once HMRC acquires new data-sharing powers expected next year.

What the Letters Actually Say

The letters are not tax demands. They are what HMRC calls "nudge" communications: a prompt to review your tax affairs and correct any errors or omissions. Receiving one does not automatically mean HMRC is opening a formal investigation, but ignoring it is a significant risk.

Triggerable tax events the letters cover

The correspondence reminds recipients that UK capital gains tax can be triggered by any of the following:

• Selling crypto for sterling or another fiat currency
• Swapping one cryptoasset for another
• Using crypto to pay for goods or services
• Giving crypto away (other than to a spouse or civil partner)

Each of these is a disposal in HMRC's terms. The gain or loss is calculated by subtracting the allowable cost (your acquisition price, plus any allowable fees) from the disposal proceeds, using HMRC's pooling rules for assets of the same type.

Penalties if you don't respond

If HMRC determines that tax was owed and not paid, and the failure is found to be careless or deliberate, the penalty can rise to 100% of the unpaid amount, on top of the tax itself plus interest. Where the assets involve offshore platforms or transfers, the penalty range widens further. Voluntary disclosure before HMRC raises an assessment typically attracts a lower penalty than one made after an enquiry begins, so the timing of any corrective action matters.

The Data Powers Coming Next Year

The enforcement escalation doesn't stop at letters. HMRC is set to receive new compulsory data-sharing powers, under which offshore crypto exchanges and custodians will be required to report UK customers' information directly to the agency. HMRC has estimated this will raise £315 million by 2030.

What this means for exchange data

If you have ever held crypto on a non-UK exchange, the expectation that HMRC cannot see it is becoming increasingly outdated. The incoming regime mirrors the approach already being implemented under the OECD's Crypto-Asset Reporting Framework (CARF), which the UK has committed to adopt. Under CARF, exchanges in participating jurisdictions will automatically exchange account-holder information with the tax authorities of the account-holder's country of residence.

In short: the data gap that allowed gaps in reporting to go undetected is closing quickly, and HMRC is acting on existing data now while deploying more powerful tools from next year. The 81,000 letters are the opening act, not the full enforcement programme.

What UK Crypto Holders Should Do Now

Whether or not you've received a letter, the scale of HMRC's campaign is a reason to review your position. Here's a practical checklist.

Step 1: Gather your transaction history

Pull complete records from every exchange and wallet you have used, including offshore platforms. You need purchase dates, disposal dates, sterling values at the time of each transaction, and any fees paid. HMRC requires you to use the actual sterling value on the date of the transaction, not an average or estimate.

Step 2: Calculate your gains and losses correctly

HMRC applies a specific pooling method (the "section 104 pool") to cryptoassets of the same type, along with same-day and 30-day "bed and breakfasting" rules that override straightforward pooling in certain circumstances. Getting this wrong is a common source of errors in self-assessment returns. A proper crypto tax report needs to reflect these rules accurately.

Step 3: Use a crypto tax calculator built for HMRC rules

A dedicated crypto tax calculator that applies HMRC's pooling and matching rules can save significant time and reduce the risk of miscalculation. The output should be a gain/loss summary per tax year that you can enter into your Self Assessment return, or hand to an accountant to review. If you're also newly within Making Tax Digital for Income Tax, our guide on what UK crypto holders must do under MTD explains how quarterly reporting interacts with your crypto obligations.

Step 4: Consider a voluntary disclosure if you have underpaid

If your review reveals that you have under-reported gains in prior years, a voluntary disclosure through HMRC's official disclosure facility is almost always preferable to waiting for HMRC to raise an assessment. Penalties for prompted disclosures are typically lower, and interest stops accruing on the tax due from the date of payment.

Step 5: Don't ignore the letter

If you have received a nudge letter and you believe your tax affairs are already in order, you still need to respond. Keep evidence of your Self Assessment submissions and any supporting calculations. HMRC's guidance on how to verify that a contact is genuine (and not a scam) is covered in our article on how to tell if an HMRC letter is real.

The Broader Picture: HMRC's Crypto Compliance Push

The 81,000 letters sit within a wider pattern of HMRC treating cryptoassets as a mainstream compliance priority. The agency has already begun including cryptoasset gains in its official capital gains tax statistics for the first time, signalling an institutional commitment to tracking this asset class alongside shares and property. The combination of improved internal data, incoming CARF reporting, and an explicitly stated revenue target of £315 million creates an enforcement environment that is meaningfully different from even two years ago.

MPs from the crypto and digital assets all-party parliamentary group have separately written to UK banks to raise concerns about banking restrictions on crypto firms, arguing these could represent a significant barrier to sector growth. But that lobbying does not affect HMRC's compliance obligations, which run in parallel.

The core message for any UK resident who has held, traded, or disposed of crypto since 2022 is the same: the tax framework has not changed, but HMRC's ability to enforce it has improved dramatically and will improve further. Getting your records in order now, whether or not you've had a letter, is the most straightforward way to reduce your exposure.

Frequently Asked Questions

I received an HMRC nudge letter about crypto. Does this mean I'm under investigation?

Not necessarily. A nudge letter is a prompt to check your tax affairs, not a formal enquiry notice. HMRC sends them to large numbers of people it believes may have underpaid, based on data it holds. You should review your returns, but receiving a letter is not itself a finding of wrongdoing.

What triggers capital gains tax on crypto in the UK?

Any disposal does: selling for fiat, swapping for another cryptoasset, using crypto to pay for something, or gifting it to anyone other than a spouse or civil partner. Income tax, rather than CGT, applies to mining rewards, staking income, and certain airdrops received in exchange for a service.

How far back can HMRC go?

For innocent errors, HMRC can generally amend assessments up to four years back. For careless errors the window extends to six years, and for deliberate non-compliance it can reach twenty years. This means gains from earlier in the bull run are still within scope.

What are the penalties for unpaid crypto tax?

Penalties depend on the behaviour HMRC determines caused the shortfall. A careless error can attract a penalty of up to 30% of the unpaid tax; deliberate concealment can go up to 100%, and higher still where offshore assets are involved. Interest accrues on the unpaid tax separately from any penalty. Voluntary disclosure before HMRC opens a formal enquiry generally results in a lower penalty.

Do I have to report crypto losses as well as gains?

Yes, and it's worth doing so. Losses can be offset against gains in the same tax year or carried forward to reduce gains in future years. They must be claimed within four years of the end of the tax year in which the loss arose. A crypto tax calculator that applies HMRC's pooling rules will identify losses as well as gains across your full transaction history.

Source: Protos