# Section 104 pooling and the 30-day rule — UK crypto tax

Group each token type into a pool with an average cost. When you sell, deduct a proportion of the pooled cost. If you buy the same token within 30 days of selling, special matching rules apply before the pool.

## Key facts
- Each token type has its own separate pool.
- The pool uses an average (Section 104) cost.
- Same-day rule: sales match buys on the same day first.
- 30-day rule: sales can match buys in the next 30 days.
- Keep a running log — spreadsheets help.

## Section 104 pooling in plain English

Imagine you buy 1 bitcoin at £20,000 and later 1 bitcoin at £40,000. Your pool has 2 bitcoins costing £60,000 total — average £30,000 each. If you sell 1 bitcoin, your allowable cost is £30,000, not the price of the first or last purchase.
## Same-day and 30-day rules

If you sell and buy the same token on the same day, those transactions match first. If you sell and rebuy within 30 days, the rebuy can match the sale instead of the pool — this stops people selling at year-end for the allowance then immediately rebuying. HMRC's Cryptoassets Manual explains the calculation order.
## Worked example: a partial 30-day match

Before selling, Morgan’s pool contains 10 ETH with a £10,000 allowable cost. Morgan sells 4 ETH for £8,000 and buys 1 ETH for £1,500 ten days later. Assume no same-day transactions, fees or other relevant acquisitions. Match 1 ETH to the £1,500 acquisition and 3 ETH to £3,000 of pooled cost. The gain is £3,500. The unmatched pool retains 7 ETH at £7,000; the matched repurchase does not enter it.

Partial matching example, before fees

| Part of disposal | Units | Allowable cost |

| --- | --- | --- |

| 30-day acquisition | 1 ETH | £1,500 |

| Section 104 pool | 3 ETH | £3,000 |

| Total | 4 ETH | £4,500 |

| Gain on £8,000 proceeds | — | £3,500 |
## One pool across wallets, not one pool per exchange

Where the same type of token is held in the same capacity, changing exchange or wallet does not create a new pool. Unique NFTs and tokens with different rights need separate analysis. Check acquisition history across all accounts before relying on a per-exchange profit report.

Source: [HMRC: pooling](https://www.gov.uk/hmrc-internal-manuals/cryptoassets-manual/crypto22200)

## Visual explanation
Match disposals in the right order
01. Same day: Match eligible purchases on the disposal date.
02. Next 30 days: Then match eligible purchases in the following 30 days.
03. Section 104 pool: Use pooled allowable cost for the remaining units.
Apply the rules in order for the same token type and capacity. A purchase already matched to a disposal does not also enter the pool.

## FAQs
### Does swapping bitcoin for ethereum use pooling?

Yes for the disposal — you sell bitcoin from its pool and acquire a new ethereum pool at the sterling value on the day of the swap.

## Sources

- [HMRC — Cryptoassets Manual](https://www.gov.uk/hmrc-internal-manuals/cryptoassets-manual)

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— Digital Assets UK (https://digital-assets.co.uk/tax/pooling-section-104-rules/), reviewed 2026-09-30. Source: https://www.gov.uk/hmrc-internal-manuals/cryptoassets-manual