Same-Day and 30-Day Pooling means a sale, gift, spend or crypto-to-crypto swap may not use your oldest coins. UK crypto disposals are matched in a strict order: same-day acquisitions first, purchases made in the following 30 days next, then your Section 104 pool.
Apply HMRC’s mandatory matching order
Match each crypto disposal in HMRC’s required order, then calculate the gain or loss.
Match same-day units first
Match all acquisitions of the same token made on the disposal date before using any other rule. If you buy 0.10 BTC and sell 0.70 BTC on 10 March, the 0.10 BTC purchase is matched first, even if the sale happened earlier in the day. Add allowable direct buying fees to acquisition cost and deduct allowable direct selling fees from disposal proceeds.
Check the next 30 calendar days
Match any remaining disposal quantity to acquisitions made in the next 30 calendar days, earliest purchase first. This bed and breakfasting rule applies to gains and losses and looks forward, not backwards: a sale on 10 March can be affected by a purchase on 5 April. Check every exchange and wallet you beneficially own, because an acquisition on another platform can fall within the window.
Use the section 104 pool last
Use the Section 104 holding only after same-day and 30-day matches are exhausted. The pool combines unmatched acquisitions of the same fungible token into one running quantity and pooled allowable cost. Its average cost is pooled cost divided by pooled quantity; if a pool holds 1 BTC costing £20,000, a 0.1 BTC disposal matched to it has an allowable cost of £2,000.
| Rule | Period checked | Order | Common mistake |
|---|
| Same-day rule | Disposal date | First | Using the pool immediately |
| 30-day rule | Next 30 calendar days | Second | Looking backwards only |
| Section 104 pool | Unmatched balance | Last | Treating it as optional |
Reconcile every bitcoin fraction in one ledger
Build one date-ordered ledger and allocate every Bitcoin fraction before reporting the result.
Enter the transactions before matching
Record the exact date, token quantity, sterling value and direct fee for every transaction. Assume an investor held 1.000 BTC in a Section 104 pool costing £20,000 before March, bought 0.100 BTC on 10 March for £3,200, sold 0.700 BTC that day for £21,000 with a £100 fee, bought 0.200 BTC on 25 March for £7,000, and bought 0.300 BTC on 5 April for £10,500. The 5 April purchase is 26 days after the sale and therefore falls within the 30-day rule despite the tax-year boundary.
Allocate the 0.700 BTC disposal
Assign the sold 0.700 BTC across the mandatory rules in sequence. Match 0.100 BTC to the same-day acquisition costing £3,200, 0.200 BTC to the 25 March purchase costing £7,000, and 0.300 BTC to the 5 April purchase costing £10,500. The remaining 0.100 BTC comes from the pool at £2,000, so total allowable cost is £22,700; net proceeds are £20,900 after the selling fee, creating a capital loss of £1,800.
Keep a worksheet HMRC can follow
Use a row-by-row worksheet so another person can reproduce your calculation. Keep records supporting acquisition and disposal values, including dates, quantities, sterling values, fees, exchange details and wallet evidence.
| Date | Transaction | BTC | Rule and assigned cost | Pool after row |
|---|
| 10 Mar | Sale | 0.100 | Same day, £3,200 | 1.000 BTC, £20,000 |
| 10 Mar | Sale | 0.200 | 25 Mar, £7,000 | 1.000 BTC, £20,000 |
| 10 Mar | Sale | 0.300 | 5 Apr, £10,500 | 1.000 BTC, £20,000 |
| 10 Mar | Sale | 0.100 | Section 104, £2,000 | 0.900 BTC, £18,000 |
Build a full matching worksheet for uneven trades
A usable UK crypto cost matching worksheet should show each acquisition and disposal as its own row, rather than splitting only the sale into matching lines. Include date, token, quantity, sterling value, proceeds, direct fee, matching rule, allowable cost, gain or loss, and the Section 104 pool quantity and pooled allowable cost after the row. For example, where a 0.700 BTC disposal is followed by acquisitions of 0.120 BTC, 0.080 BTC and 0.250 BTC within 30 days, allocate those acquisitions in date order before taking the unmatched 0.250 BTC from the pool.
If there is another cryptocurrency disposal before the 30-day window closes, record it separately and test its own same-day and future-acquisition matches. This makes the audit trail for each disposal clear.
Keep records that support the sterling calculation
For HMRC crypto tax and Bitcoin tax reporting, retain enough source evidence to recreate both the transaction and its GBP valuation. For every entry, save the date and timestamp, token and quantity, exchange or broker name, wallet addresses, transaction hash, GBP market-value source, direct trading fee and the asset used to pay that fee. Keep trade confirmations for crypto-to-crypto swaps as well as bank records where fiat was involved. Evidence of beneficial ownership matters when assets move between wallets, because a transfer under the same ownership is normally not a disposal.
Retain records showing whether a wallet, exchange account or platform position was yours, jointly held, or controlled for somebody else, and reconcile exported exchange data against on-chain transactions.
Record swaps, fees and rewards correctly
Classify each transaction before adding it to your matching ledger.
Treat a token swap as two entries
Enter a Bitcoin-to-Ether swap as a Bitcoin disposal and an Ether acquisition on the same date. Record its sterling market value, which helps calculate Bitcoin proceeds and becomes the acquisition cost of the Ether received, subject to direct fees. Apply matching rules separately to each token type; do not label a swap as an internal transfer merely because no pounds reached your bank.
Add fees and reward costs with care
Include direct trading fees on the side of the calculation to which they directly relate. Buying fees can increase acquisition cost and selling fees can reduce proceeds, while general subscriptions are usually not direct costs of a disposal. Staking rewards may have Income Tax consequences on receipt, and their sterling value may become relevant when the tokens are later disposed of.
Establish the cost of staking rewards and airdrops
Tokens received through staking or an airdrop need a receipt-date record before they can be matched on a later disposal. Staking rewards can have Income Tax consequences when received; where an amount is charged to Income Tax, that taxed sterling amount is generally relevant to the token's allowable cost for Capital Gains Tax purposes. Airdrops are fact-sensitive: receipt is not automatically taxable as income, particularly where nothing is provided in return, but an airdrop connected with services or another activity can have a different treatment.
Record the receipt date, quantity, sterling value, programme terms and any work or action required. Once acquired, fungible reward tokens enter the normal same-day rule, 30-day rule and Section 104 pool process for their token type.
Avoid false shortcuts and preserve losses
Keep a calculated capital loss unless the matching rules legitimately alter its allowable cost.
Separate UK matching from US wash sales
The UK bed and breakfasting rule changes asset matching, while a US wash sale rule focuses on loss disallowance. A later acquisition can set the cost of an earlier UK crypto disposal whether it creates a gain or loss. The rule can also cross the 5 April boundary, so a purchase in the next tax year may affect a late-March sale.
Know when this worksheet stops applying
This pooling method is mainly for fungible tokens of the same type, not every crypto transaction. NFTs are normally individually identifiable assets and do not usually enter a Section 104 pool like Bitcoin. Check dates, quantities, GBP values, direct fees, transaction IDs, beneficial ownership evidence, and staking or airdrop details before filing.
What people ask
Does pooling affect capital gains tax?
Yes. Same-day and 30-day matches can replace the Section 104 average cost, changing the taxable gain or allowable loss.
Should frequent traders use these rules?
Yes, if they are UK tax residents disposing of fungible cryptoassets personally. Review every platform and wallet.
Can I choose my matched disposal?
No. HMRC’s order is same day first, the following 30 days second, then the Section 104 holding.
What costs can I include for crypto?
Direct purchase fees can increase acquisition cost and direct sale fees can reduce proceeds. A monthly subscription is normally not direct.
Does a later tax year purchase count?
Yes, if it occurs within 30 calendar days after the disposal, even across the UK tax-year end.
Are crypto-to-crypto swaps taxable?
Usually, yes. A Bitcoin-to-Ether swap normally creates a Bitcoin disposal and Ether acquisition at its sterling value.
Is moving bitcoin to my own wallet taxable?
Usually not, provided beneficial ownership stays the same. Keep wallet addresses and transaction IDs as evidence.
Check the order before filing
Rebuild the matching order before trusting the final tax number. Start with same-day acquisitions, test every purchase in the following 30 days, then use the Section 104 pool for the remainder. Where records are incomplete or transactions involve DeFi, lending or wrapped assets, obtain UK crypto tax advice before filing.
⚠️ Do not file a pool-only calculation until you have checked purchases on every account on the disposal date and during the following 30 days.
Further reading
If you want to learn more about this topic, these sources may interest you:
