One pool for each token
CRYPTO22200 explains pooling under TCGA 1992 section 104. Where tokens are of a nature to be dealt in without identifying the particular unit, they are pooled. Bitcoin is one pool. Ether is another. A third coin is a third pool. Each pool has its own allowable cost, which rises when you acquire and falls when you dispose.
You do not pick the specific coin you “meant” to sell if the tokens are fungible. The statute does that matching for you. That is why two people with the same sale price can have different gains: their pools were built from different histories.
NFTs are the clear exception in the same page of the manual. They are separately identifiable, so they are not pooled, and the share-matching rules are not applied. Each NFT keeps its own acquisition cost. A collection of fifty NFTs is fifty assets, not one blended pool.
The order of matching
Disposals of pooled tokens are identified in a set order, the same family of rules that applies to shares:
- Same-day acquisitions. Tokens acquired on the day of the disposal are matched first.
- Acquisitions in the next 30 days. This is the rule that catches a sale followed quickly by a buy-back.
- The section 104 pool. Everything that remains is matched against the blended pool.
The 30-day rule is why “selling to use the exempt amount and buying back next week” does not behave like a clean reset. The disposal is matched to the new acquisition if it falls in that window, and the gain or loss is computed against that cost, not against the old pool. The old pool is still there afterwards. The arithmetic just refused the shortcut.
A worked sketch of that sequence is in the examples.
Allowable cost, in sterling
Each acquisition enters the pool at its sterling cost, including incidental costs of buying that belong to the acquisition. A disposal takes out a proportion of the pooled cost. Fees charged on the way out are generally incidental costs of the disposal, not a reduction of the proceeds and also a deduction, which would be counting them twice. Pick the treatment that matches the fee and apply it once.
Rewards that were taxed as income enter at the sterling value that was income, not at nil, and not at whatever the token is worth on 5 April. Airdrops that were not income and cost nothing may enter at nil. Getting that entry wrong shifts every later disposal of that token.
There is no single official HMRC price feed. Use a reasonable sterling rate at the time of the transaction and write down the source. Consistency across a year matters more than shopping for the most flattering minute of the day. If a platform shows a price in dollars, convert the dollars as well. The return is in pounds.
What a usable record contains
- Date and time, with the time zone stated once and then kept.
- Asset, quantity, and whether the units were bought, sold, swapped, spent, gifted, rewarded, airdropped or forked.
- Sterling value, the currency it was converted from, and the rate source.
- Fees, in sterling or in tokens, and which side of the computation they sit on.
- The platform or wallet, and a transaction identifier where one exists.
- For a transfer between your own wallets, a note that it was not a disposal, so a later reader does not invent a trade.
- For a DeFi deposit, whatever you can keep of the terms that show who could deal with the tokens.
Exports from exchanges are a start. They are often incomplete: missing the years before that account, missing a decentralised wallet, and describing rewards in a column that is easy to import as if it were a purchase for nil. Reconcile the export to the wallets. Do not treat a CSV as a tax computation because it has a column called “gain”.
How long to keep it
Self Assessment record-keeping periods depend on whether you filed on time and whether you have business or property income. GOV.UK sets out the periods, including a longer period where the return is late or the income is from a trade or property. Crypto histories are awkward because the pool is cumulative. A five-year-old buy is still inside this year’s allowable cost. Keep the acquisition evidence for as long as units from that acquisition, or their pooled descendants, can still affect an open year, and at least for the statutory period that applies to you. If you are unsure which period applies, keep the longer one and read the current GOV.UK page on keeping records rather than a screenshot of it.
Reconstructing a gap
If a platform has closed, start from what you still have: email receipts, bank payments in and out, blockchain transaction identifiers, and old exports. Estimate only where the evidence runs out, record that it is an estimate, and say how you made it. An estimate labelled as an estimate is a different thing from a round number presented as a download. Where the gap is large and the years are late, the disclosure route mentioned in the reporting note is more useful than a tidy fiction.
