Crypto exchanges have been sharing information with HMRC for some time.
The Crypto Asset Reporting Framework, known as CARF, takes this further by creating a formal reporting framework for cryptoasset service providers. From 1 January 2026, UK reporting cryptoasset service providers must collect specified user details and information about reportable transactions, with the first reports due to HMRC in 2027.
This article explains what UK crypto investors should know, why HMRC may have more structured data in future, and why reviewing crypto records before HMRC asks questions is becoming increasingly important.
What is the Crypto Asset Reporting Framework?
The Crypto Asset Reporting Framework, known as CARF, is an international reporting framework for cryptoasset activity.
The OECD developed CARF to help tax authorities receive and exchange information about cryptoasset users and transactions. The UK has adopted the framework, so certain cryptoasset businesses must collect information and report it to HMRC.
For further background, you can read the OECD Crypto Asset Reporting Framework FAQs and HMRC guidance on reporting cryptoasset user and transaction data.
CARF does not create a new crypto tax or change how cryptoassets are taxed in the UK. Instead, the framework gives HMRC a more structured way to receive information about cryptoasset activity.
The rules mainly affect cryptoasset service providers, such as platforms and businesses that carry out reportable cryptoasset transactions for users. However, individual investors should still understand the change because the information reported may give HMRC a clearer view of their crypto activity.
For UK crypto investors, the key issue is not whether CARF changes the tax rules. It does not. The key issue is whether their own records are complete enough to explain the figures reported on their tax return if HMRC later asks questions.
What information does the Crypto Asset Reporting Framework cover?
CARF focuses on cryptoasset activity carried out through reporting cryptoasset service providers.
Platforms may need to report information about the user, their tax residence, the cryptoassets involved and reportable transaction summaries or categories. This can include information concerning acquisitions, disposals, exchanges and transfers involving reportable cryptoassets. It is not a complete transaction-level UK tax computation.
For UK crypto investors, HMRC may receive more structured information about activity taking place through exchanges and other in-scope cryptoasset platforms.
However, CARF data may still only show part of the picture.
A platform may not know whether an investor moved assets between their own wallets. It may not hold the full history from other exchanges or wallets. The platform may not know the correct acquisition cost if the investor originally bought the asset somewhere else. It may also not understand the wider UK tax treatment of DeFi activity, NFTs, rewards, airdrops or historic transactions.
This is why CARF data and a UK crypto tax calculation are not the same thing.
CARF may help HMRC identify cryptoasset activity, but the investor still needs records that explain how they calculated the figures on their Self Assessment tax return.
Why CARF could lead to more HMRC questions
CARF gives HMRC another source of information about cryptoasset activity.
If HMRC receives data from a cryptoasset platform, it may compare that information with what the taxpayer reported on a Self Assessment tax return. If the figures do not appear to match, HMRC may ask questions.
A mismatch does not automatically mean the tax return is wrong.
A good explanation may exist. For example, the platform data may include transfers between the investor’s own wallets, transactions later matched with costs from another exchange, or activity already included within a wider crypto tax calculation.
The issue is whether the investor can explain the difference.
If HMRC asks about cryptoasset activity, the taxpayer should be able to show how they prepared the return, what records they used, and why the figures reported are supportable.
Weak crypto records can cause problems at this stage. Even where the tax position is reasonable, the taxpayer may struggle to respond properly if the underlying records are incomplete, inconsistent or unclear.
The ICAEW has also commented that CARF works more as a risk assessment tool for HMRC than as a tool that calculates tax liabilities. You can read its overview here: ICAEW: why the crypto asset reporting framework matters.
Why crypto records matter under the Crypto Asset Reporting Framework
The Crypto Asset Reporting Framework does not create the need for good crypto records. That requirement already exists.
However, CARF may make poor records harder to ignore.
If HMRC receives information showing cryptoasset activity, the taxpayer may need to explain how they reported that activity, why they did not report it, or why the figures on the tax return differ from the information HMRC holds.
That explanation depends on the records available.
For crypto investors, good records usually need to cover all relevant wallets, exchanges and platforms. They should also explain transfers, disposals, income, acquisition costs, fees, losses and any estimates or assumptions used.
Weak records can create issues such as missing acquisition costs, negative balances, duplicated transactions, unsupported losses, omitted income or gains that the taxpayer cannot properly explain.
The longer these issues remain unresolved, the harder they can be to fix. A missing wallet from three years ago may affect the cost basis of a disposal in the current tax year. An incorrect transfer may distort later gains. A historic data gap may carry forward into future calculations.
CARF should therefore act as a prompt to review crypto records before HMRC asks questions.
Why investors should not wait for HMRC to contact them
If a crypto investor knows their records are incomplete, or thinks earlier tax years may contain errors, they should usually review the position before HMRC gets in touch.
Once HMRC contacts a taxpayer, the position can become more pressured. There may be deadlines to meet, questions to answer and several years of records to review at once.
A proactive review gives the investor more control.
It allows them to check which tax years are affected, whether gains or income were missed, whether they should have claimed losses, and whether the available records are strong enough to support the figures.
If the taxpayer needs to correct a tax position, the right route will depend on the facts. Some issues may be corrected by amending a tax return. Older or more complex issues may require a disclosure to HMRC.
Any correction should rely on clear, supportable figures.
CARF increases the chance that HMRC may receive more structured cryptoasset data in future. Investors do not need to panic, but they should not ignore historic gaps or unsupported figures.
What should UK crypto investors review?
UK crypto investors should start by checking that their records cover the full picture.
That means reviewing all relevant exchanges, wallets, platforms and tax years, not just the account that is easiest to access.
A practical review should consider:
- all exchanges and wallets used during the tax year
- any missing accounts or incomplete transaction history
- transfers between wallets and whether they have been matched correctly
- negative balances, missing acquisition costs or unexplained holdings
- staking rewards, airdrops or other income entries
- disposals from crypto-to-crypto trades
- DeFi or NFT activity that may need separate review
- earlier year losses and whether they were claimed or carried forward correctly
- estimates, assumptions or manual adjustments used in the calculations
The aim is not simply to produce a number. The aim is to produce a number that can be explained.
If HMRC asks questions, the taxpayer should be able to show what data they used, how they calculated the figures and why the treatment taken was reasonable.
What if earlier tax years are wrong?
Some investors may review their records and find incomplete or incorrect figures for earlier tax years.
This can happen for several reasons. A wallet may have been missed. An exchange account may not have been included. The taxpayer may have overlooked income. Losses may not have been claimed. Historic acquisition costs may also be incomplete, which can affect later disposals.
The right way to correct the position depends on the facts.
In some cases, the taxpayer may be able to amend a tax return. In other cases, they may need to make a disclosure to HMRC. The position will depend on the tax year involved, the type of error, the reason for the error and whether HMRC has already contacted the taxpayer.
Before making any correction, the taxpayer should review the figures properly. HMRC will usually expect an explanation of what went wrong, how the corrected figures have been calculated and what evidence supports the corrected figures.
Sat Tax can help with earlier year crypto tax disclosures where historic cryptoasset tax issues need to be reviewed and corrected.
How Sat Tax can help
Crypto tax records can become difficult to manage when there are multiple exchanges, missing data, DeFi activity, NFTs, historic errors or HMRC correspondence.
Sat Tax provides structured support for UK crypto investors who need to understand and report their cryptoasset tax position.
Depending on the circumstances, support may include:
- current year crypto tax reporting
- crypto record review and reconciliation
- earlier year crypto tax disclosures
- HMRC correspondence and compliance
The right starting point depends on the condition of the records and the tax years involved. Where the records are incomplete or unclear, a review or reconciliation may be needed before a tax return or disclosure can be prepared.
The aim is to help clients prepare clear, supportable figures and deal with their UK crypto tax position in a structured way.
Final thoughts
The Crypto Asset Reporting Framework gives HMRC a more structured way to receive information about cryptoasset activity.
For UK crypto investors, the main point is not that the tax rules have changed. The main point is that HMRC may have more information available when checking whether cryptoasset activity has been reported correctly.
Good records make that easier to deal with. Poor records make it harder.
Investors who have used multiple exchanges, self-custody wallets, DeFi platforms or NFT marketplaces should make sure their records are complete and supportable. Historic gaps should not be ignored, especially where earlier figures affect the current tax position.
If your crypto records are incomplete, unclear or inconsistent, it is better to review them before HMRC asks questions.
This article is for general information only and is not personal tax advice. Tax treatment depends on the facts and the law in force. See the website disclaimer.
