UK crypto pooling: the same-day rule, 30-day rule and Section 104 pool

How HMRC matches crypto disposals to acquisitions for individuals, worked through with HMRC's own numbers, and why companies differ.

2026-10-16 · 6 min read

If you or your clients are UK-taxed individuals selling crypto, the cost you set against each sale is not your choice of lot. HMRC applies a fixed matching order, and a purchase made weeks after a sale can change that sale's gain [1]. Companies follow a similar but different order [4][6].

Why matching rules exist

Fungible tokens of the same type are interchangeable, so there is no way to say which unit was sold. UK capital gains law solves this by treating identical tokens as one pooled asset with a single allowable cost, and by carving out two exceptions that are applied first [1]. Each token type has its own pool. NFTs are not pooled because each one is separately identifiable [1].

The order for individuals

• Same-day rule (TCGA 1992 s.105): all acquisitions and all disposals of the same token on the same day are each treated as one transaction, and the disposal is matched to that day's acquisitions first [1].
• 30-day rule (TCGA 1992 s.106A): any remaining disposal is matched to acquisitions of the same token in the 30 days after the sale, earliest acquisition first. This is the anti bed-and-breakfasting rule [1][5].
• Section 104 pool (TCGA 1992 s.104): whatever is left is matched to the pool at its average cost. Acquisitions not used by the first two rules enter the pool [1].

Two practical consequences follow. First, a sale is not final for tax until 30 days have passed, because a later purchase may be matched to it. Second, a token bought inside that window and matched back to an earlier sale never reaches the pool, so the pool's average cost is unaffected by it [1][2]. Under s.106A the 30-day rule does not apply to acquisitions made while the individual is not UK resident [5].

What counts as allowable cost

The pool tracks sterling cost. Allowable costs include the original price paid plus incidental costs such as fees for having a transaction added to the blockchain and exchange fees on buying or selling. HMRC's view is that a fee on a token-to-token swap is split between the two assets, and that fees for depositing or withdrawing fiat are not allowable. Costs already deducted for income tax cannot be claimed again [3].

Worked example (HMRC's Example 6)

HMRC's manual walks through all three rules interacting [2]. The individual starts with 100,000 tokens in a Section 104 pool at a cost of £300,000, then trades as follows.

Note that the 6 August purchase is used up oldest-disposal first: the 31 July sale takes its share before the 5 August sale [2]. Note also that the 7 August result could still move if more of the same token were bought within 30 days after it; HMRC's example assumes no such purchase [1][2].

Companies use a different window

For corporation tax, HMRC describes slightly different rules [4]. A company's disposal is first matched with same-day acquisitions, even if the disposal happened earlier in the day. It is then matched with acquisitions made in the previous nine days, first in first out, ahead of the pool [4]. The statutory basis is TCGA 1992 s.107, which applies to companies and refers to acquisitions and a later disposal within a period of 10 days [6]. There is no 30-day forward rule for companies [4][5].

The direction matters for systems. An individual's window looks forward, so the sale stays provisional. A company's window looks backward, so the matching can be settled on the disposal date. HMRC's company guidance is brief, and how s.107 wording maps onto every crypto fact pattern is worth confirming with an adviser.

New reporting from 2026

From 1 January 2026, UK cryptoasset service providers must collect customer details under the OECD Cryptoasset Reporting Framework, which the UK has extended to UK-resident users. The first reports, covering calendar year 2026, are due between 1 January and 31 May 2027 [7]. HMRC will therefore see more third-party data on disposals, so pool records that reconcile to exchange data matter more than before. As of October 2026, HMRC's guidance said the online submission service was not yet live [7].

What to do

• Keep a separate sterling pool per token type, and record every acquisition and disposal with a UK-time date.
• Treat individual disposals as provisional for 30 days; recompute when a matching purchase arrives.
• Do not apply the individual 30-day rule to a company; check same-day and prior nine-day acquisitions instead.
• Capture fees at the transaction level and apportion swap fees between the two tokens.
• Reconcile your pool records to exchange statements ahead of the first CARF reports in 2027.

This is general information, not tax advice.

Sources

1. CRYPTO22200 - Cryptoassets for individuals: Capital Gains Tax: pooling (HMRC)
2. CRYPTO22256 - Cryptoassets for individuals: Capital Gains Tax: pooling examples: example 6 - interaction of same day rule, 30 day rule and section 104 pool (HMRC)
3. CRYPTO22150 - Cryptoassets for individuals: Capital Gains Tax: allowable expenses (HMRC)
4. CRYPTO41350 - Cryptoassets for businesses: Corporation Tax: Corporation Tax on Chargeable Gains - pooling (HMRC)
5. Taxation of Chargeable Gains Act 1992, section 106A (legislation.gov.uk)
6. Taxation of Chargeable Gains Act 1992, section 107 (legislation.gov.uk)
7. Reporting cryptoasset user and transaction data (HMRC (GOV.UK))

General information for finance teams, current as of publication. Not legal, tax or accounting advice.

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