From 1 January 2026, the UK applies the OECD’s Crypto-Asset Reporting Framework (CARF), introducing a systematic reporting obligation for in-scope cryptoasset activity. Reporting Cryptoasset Service Providers (RCASPs), including many exchanges and other businesses that effectuate in-scope cryptoasset transactions, must collect relevant user and transaction data and report it to HM Revenue & Customs (HMRC).
Until now, HMRC’s visibility over cryptoasset activity has depended on existing tax returns, information requests, platform data and compliance checks, rather than a standardised annual reporting framework. From the 2026 calendar year, this changes. In-scope providers must apply due diligence procedures and report prescribed user and transaction information to HMRC. For UK taxpayers, the practical effect is clear: cryptoasset activity reported by platforms will become easier for HMRC to compare with Self Assessment returns.
What is CARF?
CARF is the OECD’s Crypto-Asset Reporting Framework, which the UK applies from 1 January 2026. It builds on the international model used for over a decade to exchange tax information between jurisdictions, such as the Common Reporting Standard (CRS) for bank accounts and financial instruments. Existing international reporting regimes already require financial institutions to exchange information on certain financial accounts and investment income. CARF extends this type of tax transparency framework to cryptoassets.
In practice, many cryptoasset intermediaries that previously sat outside CRS-style reporting will now have tax reporting obligations where they fall within the RCASP rules. UK Reporting Cryptoasset Service Providers must collect standardised information on users and report annually to HMRC where the user is reportable under the CARF rules.
The policy objective is to reduce tax evasion and under-reporting by giving tax authorities more structured information on cryptoasset users and transactions. The first CARF reporting period covers the 2026 calendar year, with reports due to HMRC by 31 May 2027. From there, information can be exchanged with other participating tax administrations under the CARF framework. The result is a new reporting layer that brings cryptoassets closer to the transparency standards already applied to parts of the banking and investment sector.
When does CARF take effect in the UK?
The UK confirmed its adoption of the OECD Crypto-Asset Reporting Framework and has implemented the rules through domestic legislation and HMRC guidance. From 1 January 2026, UK Reporting Cryptoasset Service Providers must start collecting user and transaction data in line with the CARF rules.
Providers must identify reportable users, collect tax residence information and keep structured records of reportable cryptoasset transactions from that date.
The first report must be submitted by 31 May 2027, covering the period from 1 January 2026 to 31 December 2026. From that point, CARF data can be exchanged with other participating tax administrations under the international framework. For UK taxpayers, this means that from 2026 in-scope platform activity will be recorded in a more structured way, and from 2027 HMRC will be able to compare reported platform data with what appears in your Self Assessment return. The next step is understanding what information appears in CARF reports, and why you still need a separate UK tax calculation for your Self Assessment return.
What data will be reported under CARF?
CARF does not only define which providers are in scope; it also sets out the categories of user and transaction information that must be reported. UK Reporting Cryptoasset Service Providers must collect and report standardised data for reportable users and transactions.
The reporting is divided into two main categories:
Client Identification
full name, date of birth, residential address, and country of tax residence;
for UK residents, this includes a Taxpayer Identification Number (typically a National Insurance Number or UTR).
Transaction details: a comprehensive log of crypto activity
exchanges: both crypto-to-fiat conversions and crypto-to-crypto swaps;
transfers: movements between different wallets or platforms;
payments: transactions involving stablecoins and, in some cases, payments made via crypto debit cards.
Special attention will be given to cash-outs into bank accounts, which are expected to become a central focus of HMRC’s compliance checks and automated cross-referencing.
The real-world impact: how HMRC uses this data
For individuals investing in cryptoassets in the UK, the core tax obligations remain unchanged: taxable gains and income must be reported through Self Assessment where a return is required. Capital Gains Tax (CGT) can apply when you dispose of cryptoassets, while Income Tax can apply where cryptoassets are received as earnings, rewards or other taxable income.
CARF does not introduce a new crypto tax. Instead, from 2026, it gives HMRC a new source of structured platform data that can be used for compliance checks and data matching.
In practice, this reduces the gap between what taxpayers report and what HMRC can verify. If platform data shows disposals, cash-outs or other reportable activity that does not align with your Self Assessment return, HMRC may be able to identify the mismatch more easily. HMRC may use this type of data to issue compliance checks or nudge letters, asking taxpayers to review or correct their position before a more formal enquiry develops.
Preparing for CARF with Finbooks
From 2026, in-scope platform data will start being collected under CARF and reported to HMRC from 2027. This means your activity on reporting platforms will become easier for HMRC to compare with what you report in your Self Assessment return.
With Finbooks, you can calculate your Capital Gains Tax position, track gains and losses, and generate organised reports of your transactions, balances and movements.
You can also create organised tax reports to support your Self Assessment submission, giving you a consistent record that can be reviewed against the data platforms report under CARF.
