The 30-day rule for crypto in the UK: bed and breakfasting explained

When you dispose of crypto in the UK, HMRC decides which cost basis to use, checking three rules in order: same-day, then 30-day, then the pool. The 30-day "bed and breakfast" rule stops you from selling at a loss, waiting a few days, and then buying back the same token at the new lower price — a strategy that would let you harvest the tax loss while resetting your cost basis. If you rebuy within 30 days of selling, the rebuy is matched to the sale at the rebuy price, and that recalculated gain or loss is the one that counts.

New to HMRC's matching rules? Start with the Section 104 pool guide, which covers all three rules in order. For tax losses specifically, see how to claim crypto losses.

What is the 30-day rule for crypto in the UK?

The 30-day rule is an automatic matching rule applied by HMRC. If you sell crypto and then buy the same token within 30 days of the sale, the repurchase is matched to the original sale, not to your pool average cost. This means your gain or loss is recalculated using the repurchase price as the cost basis, not the original purchase price.

Technically, the rule matches acquisitions in the 30 days after a disposal, in strict earliest-purchase-first order (FIFO). If you sell on 1 March and buy on 20 March and again on 25 March, the 20 March purchase is matched first, and the 25 March purchase is matched second. The rule applies automatically — you do not elect it; HMRC applies it in its calculations and audits.

It only applies to the same asset. If you sell Bitcoin and buy Ethereum, the 30-day rule does not apply — that is a different asset class.

Watch out

The 30-day window is strict: 31 days later, you have missed it

The rule applies to acquisitions in the 30 days following a disposal. If you sell on 1 March and buy on 1 April (31 days later), the purchase falls outside the window and reverts to the Section 104 pool — no 30-day matching. The day-count includes the sale date and the rebuy date, so day 1 = sale day, day 30 = the last day of the window.

Why does the 30-day rule exist (bed and breakfasting)?

The rule prevents a tax avoidance strategy called "bed and breakfast." Here is how the strategy works without the rule: You hold 100 Bitcoin bought at £10,000 each (£1,000,000 cost). Bitcoin drops to £6,000 each. You decide to: (1) Sell all 100 Bitcoin at £6,000 each = £600,000 proceeds. This crystallises a loss of £400,000. (2) Immediately rebuy 100 Bitcoin at £6,000 each = £600,000 spent. (3) You still own 100 Bitcoin, but now your cost basis is £600,000 instead of £1,000,000. You have claimed a £400,000 loss for tax, and reset your cost base to the lower market price. (4) If Bitcoin recovers to £10,000, your gain is now only £400,000 instead of zero — and the £400,000 loss is gone from your tax record.

This strategy essentially allows you to harvest a tax-valuable loss while keeping the investment — a freebie that HMRC does not allow. The 30-day rule blocks it: HMRC forces the rebuy to be matched to the sale at the rebuy price, so the loss is negated.

How does the 30-day rule change my gain or loss?

Instead of using the original purchase price (or the Section 104 pool average), the cost basis for a 30-day matched disposal is the cost of the reacquisition. This can dramatically change the gain or loss, or even flip a loss into a gain.

Worked example (HMRC CRYPTO22253)

How the 30-day rule blocks loss harvesting

You hold a token called C in your Section 104 pool. You dispose and rebuy within the window.

1 Jan: Buy 2,000 tokens C£1,000 cost

Pool average cost so far£0.50 per token

31 Mar: Sell 1,000 tokens C£400 proceeds (£0.40 per token)

Expected loss without 30-day rule1,000 × (£0.40 − £0.50) = −£100

21 Apr: Buy 700 tokens C£175 cost (within 30-day window)

28 Apr: Buy 500 tokens C£100 cost (within 30-day window)

1 May: Buy 500 tokens C£150 cost (outside the 30-day window)

The 31 Mar sale of 1,000 tokens (proceeds £0.40 each) is matched to the 30-day reacquisitions in order, earliest first. 21 Apr — 700 tokens, cost £175: matched to 700 of the sold tokens → proceeds 700 × £0.40 = £280, less £175 cost = £105 gain. 28 Apr — only 300 tokens remain to match (cost £60 for those 300, at £0.20 each): proceeds 300 × £0.40 = £120, less £60 = £60 gain. The remaining 200 tokens from the 28 Apr buy and the whole 1 May buy fall into the Section 104 pool. Result: instead of the £100 loss you expected, the 31 Mar disposal produces £165 of gains — the bed-and-breakfasting strategy is blocked.

Watch out

The 30-day rule can turn an expected loss into a gain

If you sell at a low price and rebuy at an even lower price within 30 days, the rebuy price becomes your cost basis for CGT — so the gain widens, not narrows. This is intentional: the rule is a penalty for loss-harvesting, not a reward.

Is there a wash-sale rule for crypto in the UK?

The UK does not have a separate "wash-sale rule" like the US does (IRC § 1091). Instead, HMRC uses the 30-day matching rule. The key difference: UK applies the rule to all cryptoassets and forces matching to the rebuy price. US investors (currently) can sell crypto at a loss, rebuy immediately, and claim the full loss on their US tax return. UK investors cannot — the rebuy is matched to the sale at the rebuy price, negating the loss. This is a major difference in tax strategy between the two countries.

How do the same-day, 30-day, and Section 104 rules fit together?

HMRC applies three matching rules in strict order. Each disposal is checked against each rule in turn; whichever rule matches it first is applied, and the rest falls through to the next rule. Rule 1 (same-day): Coins bought on the same day as the disposal, matched at the same-day cost. Rule 2 (30-day): Coins bought in the 30 days after (earliest first), matched at the rebuy cost. Rule 3 (Section 104 pool): Remaining coins, matched at the pool average cost.

Worked example

Same-day, 30-day, and pool all in one sale

You sell 500 BTC on 15 June. 1 Jan: Buy 1,000 BTC @ £10,000 total (Pool: 1,000 @ £10.00 avg). 15 Jun: SELL 500 BTC @ £8,000 (the disposal to match). 15 Jun: Buy 50 BTC @ £2,000 (same day). 20 Jun: Buy 100 BTC @ £1,500 (5 days after). 30 Aug: Buy 100 BTC @ £3,000 (76 days after).

Same-day (50 BTC @ £2,000)Gain = 50 × (£16 − £40) = −£1,200 loss

30-day (100 BTC @ £1,500)Gain = 100 × (£16 − £15) = £100 gain

Pool (remaining 350 BTC)Gain = 350 × (£16 − £10) = £2,100 gain

Total gain£100 + £2,100 − £1,200 = £1,000 net

Each slice uses the rule that applies to it. This is exactly how HMRC's worked examples present the figures.

How can I realise a loss without triggering the 30-day rule?

The 30-day rule only matches a rebuy of the same token within 30 days of the disposal — so the loss is realised cleanly, outside the rule, if you do any of the following:

Wait more than 30 days before buying that token back — once you're past day 30, the rebuy goes to the Section 104 pool and the loss stands.

Buy a genuinely different asset — sell BTC at a loss and buy ETH, say. A different token is a separate Section 104 pool, so the 30-day rule doesn't apply.

Move into a stablecoin — a stablecoin (USDT/USDC) is a different cryptoasset for CGT, so selling BTC at a loss into it realises the loss (note: that swap is itself a disposal, and the stablecoin then has its own cost basis).

These aren't loopholes — they simply fall outside the rule's narrow scope, which only catches a rebuy of the *same* coin. This is general information, not tax advice; if you're planning around a significant loss, check your own circumstances or speak to a qualified adviser.

How CryptoCGT handles the 30-day rule

CryptoCGT's tax engine implements all three HMRC matching rules (same-day, 30-day, Section 104) in the correct order. Our calculations have been verified against HMRC's own worked examples — specifically CRYPTO22253 (the 30-day rule example) and CRYPTO22251–22254 — and match to the penny. When you import your transactions, the engine automatically applies the 30-day rule for any disposal with a rebuy within 30 days. You do not need to do anything; the calculator handles it.

Sources

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This guide is information, not tax advice.Figures and thresholds are for the tax year shown (England, Wales & Northern Ireland; Scottish income tax bands differ). Rates and rules can change, and your own position may differ — check your circumstances and speak to an accountant before you file. CryptoCGT is an information tool, not a regulated tax adviser.