HMRC Targets Crypto Taxes as CARF Reporting Nears

HMRC issued 81,172 tax warnings to crypto investors last year, a 25% increase as the UK prepares for mandatory CARF reporting in 2026.

This campaign arrives just ahead of new international rules for automatic reporting that will grant authorities significantly greater visibility into digital asset transactions.

Over 81,000 Warnings in a Single Year

Data obtained through a UK Freedom of Information Act request, shared by Finance Feeds, reveals a major shift in the approach taken by HM Revenue and Customs (HMRC).

During the 2024/25 financial year, the administration sent out 81,172 notices to investors who they believe may have undeclared tax liabilities from crypto assets. A year earlier, that figure stood at 64,982, marking an increase of approximately 25%.

Compared to 2024, the volume of these warnings has nearly tripled.

This does not necessarily mean that tens of thousands of investors are being accused of tax evasion. These messages are part of HMRC’s practice of sending “nudge letters,” which the administration uses to encourage taxpayers to verify for themselves whether their declarations are complete.

The distinction is important. Receiving such a warning does not constitute a formal tax assessment and does not, by itself, prove a violation. However, it indicates that HMRC possesses information that may not align with the data declared by the investor.

Why HMRC is Increasing Pressure Now

The timing is no coincidence. The UK is entering a transition period after which tax authorities will have a much more structured flow of information regarding crypto asset holders and their transactions.

Starting January 1, 2026, crypto service providers in the UK began collecting information under the Cryptoasset Reporting Framework (CARF).

Developed by the OECD as an international standard for the automatic exchange of tax information on crypto assets, the framework aims to close the information gap. This gap previously allowed investors to hold or trade digital assets through platforms outside their home country without local tax administrations easily monitoring the activity.

The first reporting period covers transactions made in 2026, with UK providers required to submit the relevant data to HMRC by May 31, 2027.

This turns the current wave of warnings into more than just an isolated campaign. HMRC is effectively giving investors the opportunity to correct past omissions before the volume of data available to the administration grows significantly.

CARF Changes How Discrepancies Are Detected

The most significant change will come with the international exchange of information.

Once CARF is operational on a broader scale, data from crypto platforms in participating jurisdictions can be shared between national tax administrations. This brings crypto assets closer to the automatic reporting system that already exists for traditional financial accounts.

The practical implications are substantial. Instead of HMRC relying primarily on individual audits and information requested from specific platforms, a larger portion of the process can be automated.

Declared income or capital gains can be cross-referenced with information submitted by crypto service providers. Any discrepancies can subsequently be flagged for further investigation.

This increases the risk for investors who assume that using a foreign exchange automatically makes their activity invisible to British authorities.

Crypto-to-Crypto Trades Can Also Trigger Tax Liabilities

One reason for the high number of potential discrepancies is the complexity of UK tax treatment for cryptocurrencies.

An investor does not necessarily have to sell Bitcoin or another token for British pounds for a taxable event to occur.

Exchanging one crypto asset for another—for example, BTC for Ethereum—is generally viewed as a disposal of the first asset for Capital Gains Tax purposes. Using cryptocurrency to purchase goods or services may also constitute a disposal.

A similar principle applies to gifting crypto assets, with certain exceptions, including transfers between spouses or civil partners.

This creates a challenge, particularly for active traders. A portfolio that seemingly only contains a series of token swaps and has never been cashed out into fiat currency may still contain numerous taxable events.

DeFi and Staking Complicate the Picture

The issue becomes even more significant with staking, cryptocurrency mining, and decentralized finance (DeFi) protocols.

Depending on the specific operation and circumstances, the assets received may fall under different tax treatments. This means that determining liability is not always as simple as calculating the difference between the purchase and sale price.

DeFi adds another layer of complexity through liquidity provision, lending assets, receiving rewards, and transfers between various protocols.

Younger investors are particularly at risk of unintentional errors, as many of them actively use the crypto market without having had a reason to file more complex tax returns previously.

The Era of Limited Visibility is Ending

The jump from 64,982 to over 81,000 warnings reveals that HMRC is already using available data more actively. However, CARF could change the very scale of oversight.

Until now, tax administrations had to overcome fragmentation between exchanges, wallets, and different countries. Automated international exchange is gradually removing this information barrier.

For British crypto investors, this means the question is increasingly less about whether HMRC can obtain information on a specific transaction and more about whether the administration’s data matches their filed tax return.

The current “nudge letters” can therefore be seen as a transition toward a much more systematic oversight model, where identifying potential discrepancies will require less manual labor from tax authorities.