This is the part of accepting stablecoins that surprises people, and it surprises them at exactly the wrong moment, which is usually when their accountant asks a question they cannot answer.
You sold something. Somebody paid you. In your head that is a sale, and the story ends. In tax terms you also acquired an asset, and everything that happens to that asset afterwards is a separate story with its own rules.
Two events, not one
When a payment lands, two things happen at the same instant.
The first is trading income: the sterling value of what you supplied, in your accounts as revenue, with VAT due on it. Familiar territory.
The second is an acquisition. You now hold an asset, and its base cost is that same sterling figure. Nothing is owed on this — you have simply acquired something at a known cost.
The tax arrives later, when you dispose of it. And "dispose" is broader than it sounds.
What counts as a disposal
- Converting to sterlingThe obvious one. Cashing out is a disposal.
- Paying a supplier with itLess obvious, equally a disposal. You used the asset to settle a debt.
- Exchanging it for another assetAlso a disposal, of the first one.
- Giving it awayStill a disposal, at market value.
Moving it between your own wallets is not. That is a transfer, and treating it as income or a disposal is the single most common error in crypto bookkeeping — it inflates your revenue and invents gains that never happened.
Why you cannot just take the first one out
Here is where it stops being intuitive. You cannot pick which units you disposed of. UK rules decide for you, in a fixed order.
Same day first. A disposal matches against anything of the same type you acquired on the same day.
Then the next thirty days. Any remainder matches against acquisitions in the thirty days following the disposal — acquisitions that had not happened yet when you disposed.
Then the pool. Whatever is left comes out of the Section 104 pool, which holds everything else of that type at a single pooled average cost.
A business taking forty payments a day and paying suppliers weekly is running this calculation constantly, whether or not anyone is doing it.
Why a spreadsheet will not save you
People try. It works for a handful of transactions and falls apart at volume, for a specific reason: the thirty-day rule is retrospective.
A disposal on the 3rd may have to match against an acquisition on the 25th. So you cannot finalise the 3rd until the month has played out, and a new acquisition can change a calculation you already did. That is not a formula, it is a recalculation across the whole history every time something new arrives.
Add hundreds of small acquisitions from ordinary trading and it is not a spreadsheet job. It is a job for something that recalculates the pool every time a transaction lands, and keeps a dated record of which rule matched what.
How big are the numbers, honestly? Small. A stablecoin barely moves, so the gains and losses on ordinary trading are pennies and pounds rather than anything dramatic.
But small is not nil, and "it was only a bit" is not a filing position. The reason to do it properly is not the size of the number — it is that you cannot demonstrate the number is small without having calculated it.
What this looks like when it is handled
Every payment enters the pool at its recorded sterling cost as it arrives. Every disposal produces a dated calculation showing the matching applied, the basis used, and the resulting gain or loss. The pooled cost carries forward and is visible at any point in the year.
Your accountant gets a disposals report they can check rather than a list of transactions they have to reconstruct. That is the difference between a quiet year end and an expensive one.
Ceodore applies Section 104 pooling with same-day and thirty-day matching on every disposal, automatically, with the working shown.