What HMRC actually expects from crypto users
Not a wall of legalese: the handful of things every tax authority wants to see, and the one rule that makes United Kingdom different.
- Which moves usually count as a taxable event
- The one rule that makes United Kingdom its own case
- Why exchanges reporting to HMRC changes the math
HMRC doesn't let you pick which coins you sold — same-day and 30-day matching rules apply first, then everything else is averaged into a single Section 104 pool per token.
Relevant filing: Self Assessment.
Holding is not the problem. Disposing is.
In most tax systems, simply buying crypto and holding it is not what triggers tax. What triggers it is a disposal: selling for GBP, swapping one token for another, or spending it. That is the moment a gain or a loss becomes real, and the moment HMRC can ask you to explain it.
This is why people who 'never cashed out' still end up with something to report. If you traded BTC for ETH, you disposed of BTC — even though no GBP ever hit your bank account.
Everything hangs on one number
A gain is what you got minus what it cost you. The second half of that sentence — the cost — is where nearly every mistake lives. It depends on the price at the moment you acquired the asset, and on the method your country makes you use to match buys against sells.
That method is not a detail. It is the difference between two very different results from the exact same trades.
The exchanges are already talking
The era of assuming nobody sees your trades is closing. Reporting frameworks are being rolled out internationally, and exchanges increasingly hand transaction data to tax authorities directly. Your job is no longer to be invisible — it is to have numbers that match.
The practical takeaway: keep a clean, complete record now, so that whatever arrives at HMRC from a third party lines up with what you filed.
