Crypto-to-crypto: the trade people forget to report
You swapped ETH for USDT and no money touched your bank. In most systems, you still just disposed of an asset.
- Why a swap is usually two events, not zero
- Stablecoins are not a safe harbour by default
- How to price a swap when no GBP was involved
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.
No bank movement, still a disposal
The intuition that 'it isn't real until I cash out' is the most expensive intuition in crypto. In most tax systems, exchanging one asset for another is a disposal of the first one — the fact that you received another token instead of GBP doesn't undo it.
So a single swap can create a gain or loss on the asset you gave up, measured in GBP, even though your bank never saw a cent.
Stablecoins don't switch the rules off
Moving into USDT or USDC feels like parking in cash. Legally, in most places, it is still a disposal of whatever you sold to get there — a stablecoin is an asset, not your national currency.
That is why people with heavy stablecoin activity are often the most surprised at how much there is to report.
Pricing a trade that had no price tag
If no GBP appeared, you still need a GBP value for both sides at the moment of the swap. The market value at that timestamp is what makes the gain computable.
Done by hand, this is where spreadsheets die. Done properly, each swap is converted at the price of its own date and the arithmetic stays visible.
