30-day rule crypto UK 2026: bed and breakfasting explained

The UK's 30-day rule (often called bed-and-breakfasting) reshuffles the cost basis of any cryptoasset you sell and rebuy within 30 days. For 2026 it applies to every disposal — including DeFi swaps and stablecoin rotations — and is the single biggest reason simple FIFO calculations produce the wrong answer for UK filers.

What is the 30-day rule for UK crypto?

The rule is also one of the most misunderstood parts of UK crypto tax. Most US-based articles describe a wash-sale rule that does not quite map onto the UK version. The UK rule is wider in some ways (it catches all losses and gains, not just losses) and narrower in others (it only applies to the same asset, not "substantially identical" assets as in the US). Getting it right matters because every tool that defaults to FIFO will produce numbers that do not match what HMRC expects.

Why HMRC has this rule

Section 105 of the Taxation of Chargeable Gains Act 1992 was written to stop a 1990s tactic where investors sold shares on 5 April, crystallised a loss against that year's gain, and rebought them on 6 April — keeping the position open while harvesting the tax loss. HMRC closed the loophole by saying any rebuy within 30 days is matched against the sale, neutralising the artificial loss.

The same rule applies to cryptoassets because HMRC treats them as property under TCGA 1992, with the same share-pooling and matching framework as listed shares. The economic substance is identical: a round-trip in and out of the same exposure should not magic up a deductible loss.

The share-matching order

For every disposal, HMRC matches in this strict sequence:

1. Same-day rule — any acquisitions of the same asset on the same calendar day match first, at their actual acquisition cost.
2. 30-day rule — any acquisitions of the same asset made in the 30 days after the disposal match next, at their actual acquisition cost. They do not enter the Section 104 pool at all.
3. Section 104 pool — anything still unmatched comes out of the pool at the weighted-average cost.

The order is not optional. A tool that uses FIFO, LIFO or HIFO is producing a US calculation, not a UK one. For more on how share-pooling ties everything together, see our UK crypto tax calculator walk-through.

Worked example

Daniel holds 10 ETH in his Section 104 pool at an average cost of £1,000 per ETH (total pool value £10,000). He makes the following moves:

The 5 ETH bought on 15 May are within 30 days of the 10 May disposal. Under the 30-day rule they match against the sale, not the pool.

Disposal calculation:
Proceeds: 5 × £2,000 = £10,000
Cost basis (matched to 15 May rebuy): 5 × £1,800 = £9,000
Gain = £1,000

Crucially, Daniel's Section 104 pool is unchanged. It still contains 10 ETH at £1,000 each. The 5 ETH he sold and rebought effectively bypassed the pool entirely. If he had instead waited until 11 June 2026 to rebuy, the disposal would have used the pool basis (£1,000 per ETH) and produced a £5,000 gain — five times higher.

Now compare the same trades but with a fall in price:

Daniel hoped to crystallise a £500 loss against pool basis (£1,000 - £900 = £100 × 5). The 30-day rule kills the strategy:

Proceeds: 5 × £900 = £4,500
Cost basis (matched to 20 May rebuy): 5 × £950 = £4,750
Loss = £250, not the £500 Daniel had hoped for. The Section 104 pool is unchanged. The other £250 of unrealised loss is still trapped in the pool until Daniel actually sells without rebuying.

One subtle effect: in a falling market, the 30-day rule can actually flip the sign of an outcome. A pool basis of £1,000 per ETH and a sale at £1,200 looks like a £200 gain. If you rebuy at £1,100 within 30 days, the matched basis becomes £1,100 and the gain is cut to £100. The rule is not always punitive — it just removes choice. Every tool needs to apply it consistently regardless of whether the result is in your favour.

Why this matters for loss harvesting

UK crypto investors cannot replicate the US wash-sale dodge of selling for a loss and rebuying immediately. To harvest a loss cleanly you have to actually exit the position for at least 31 days, accept the market risk during the gap, then rebuy. Most losses get crystallised toward the end of the tax year (late March), with rebuys planned for early May to be safe.

For the bigger picture on what losses can do for you, see our piece on claiming crypto losses on UK Self Assessment.

DeFi and crypto-specific gotchas

DeFi adds complications that did not exist when TCGA 1992 was drafted. The headline gotchas:

• Liquidity-pool entries and exits. Depositing ETH into a Uniswap V3 pool is generally treated as a disposal of ETH for LP tokens. Withdrawing reverses the swap. If you re-enter within 30 days, the 30-day rule could match the deposit and the re-deposit, depending on the substance of the position.
• Token swaps via routers. A 1inch route that goes ETH → USDC → DAI is two disposals of two assets, not one. Each leg carries its own 30-day window.
• Yield farming auto-compounds. Each compound is a fresh acquisition of the underlying. If you sold the same token elsewhere within 30 days, the auto-compound matches the sale — even though you never consciously rebought.
• NFTs. Each NFT is its own asset (a unique token-id), so the rule almost never bites. Buying a different NFT from the same collection is not a rebuy.

Stablecoins, wrapped tokens and forks

HMRC's position on what counts as "the same asset" is clearer for some cases than others.

• Stablecoins. USDC and USDT are different assets even though they both target $1. Rotating from USDC to USDT does not trigger the 30-day rule on either token. This is a legitimate way to maintain stable exposure while harvesting a loss on a depegged stablecoin.
• Wrapped ETH. Treat WETH as the same asset as ETH for the rule. Wrapping and unwrapping is contentious; the conservative approach is no disposal on wrap, no disposal on unwrap, and the WETH position counts toward the same Section 104 pool. Document your method.
• Bridged tokens. Bridging USDC from Ethereum to Base may be a disposal if the bridged token is technically a different contract. Many tools class native and bridged USDC as the same asset; HMRC has not given specific guidance. Conservative treatment mirrors how you treated WETH.
• Hard forks and airdrops.Forked tokens (BCH from BTC, ETH-PoW from ETH) are new assets with their own pool and their own 30-day windows. HMRC's Cryptoassets Manual sets out the allocation of cost basis between the original and the fork.

Legitimate workarounds

You cannot opt out of the 30-day rule, but you can plan around it:

• Wait the full 31 days. The cleanest, most defensible approach. Set a calendar reminder for the day after the window closes.
• Spousal transfer. Transfers between spouses or civil partners are no-gain-no-loss; your spouse takes over your cost basis. They can sell at their own AEA and at potentially a lower rate. The 30-day rule does not stop this if the trades are genuinely separate.
• Switch correlated assets. Sell ETH and buy SOL or a Layer-2 ETH variant. Different asset, no matching, but you keep broadly equivalent crypto-market exposure.
• Rotate stablecoins. If you held a stablecoin that depegged and want to harvest the loss, sell into a different stablecoin (USDC into USDT, for example). HMRC treats them as different assets.
• Use an ISA-eligible wrapper. Crypto itself is not ISA-eligible, but spot Bitcoin and Ethereum ETPs listed on the London Stock Exchange became eligible in 2024. Inside an ISA there is no CGT and no need to worry about the 30-day rule at all.

Record-keeping for 30-day matches

The 30-day rule lives or dies on the quality of your records. HMRC wants to see, for any disposal that bumped against the rule:

• The date and GBP value of the disposal.
• Every acquisition of the same asset in the 30 days that followed, with date and GBP cost.
• The order in which you matched units to the same-day rule, the 30-day rule and the pool — including a unit-by-unit breakdown.
• The state of the Section 104 pool before and after the disposal, showing any units that bypassed the pool because of the 30-day match.

On a busy DeFi year this is unmanageable by hand. A dozen swaps a day across three chains can produce hundreds of 30-day matches in a single tax year. Pulling each one into a spreadsheet and checking the matching order is roughly a full week of work. Specialist tools such as Koinly run the share-matching automatically and produce an auditable transaction-by-transaction report. The output mirrors the format HMRC expects in an enquiry, which is the difference between spending an afternoon answering questions and spending a month.

If HMRC opens an enquiry

HMRC opens around five thousand crypto enquiries a year as of 2026, most of them prompted by data feeds from CARF and historical exchange information notices. The 30-day rule is high on the list of things examiners check, because it is mechanical and easy to miscalculate. If you receive a Schedule 36 information notice or a Code of Practice 8 letter, expect them to ask for:

• Full transaction history for every wallet and exchange you used in the year under enquiry.
• A reconciliation showing how your declared gain was built — pool basis, same-day matches, 30-day matches and any costs deducted.
• The source of every GBP price used, especially for crypto-to-crypto swaps where there was no fiat leg.
• Evidence that any losses claimed were not artificially harvested via a rebuy that the rule should have neutralised.

If your records are clean, an enquiry usually closes within a few months with no adjustment. If they are not, expect HMRC to disallow contested losses, recompute the gain using the share-matching order and apply behavioural penalties of 0 to 30% on top. Engage a chartered tax adviser the moment a formal letter arrives. Read our guide to claiming crypto losses with HMRC before responding to any loss-related question.

The official source is HMRC's Capital Gains Manual on share-matching rules. For the broader UK framework, see the UK crypto tax guide and our deadline reference at HMRC Self Assessment crypto deadlines.