The UK 30-day rule for crypto (bed-and-breakfasting) explained — 2026

The single rule that catches out more UK crypto investors than any other is the 30-day rule — TCGA 1992 s.106A, often called the “bed-and-breakfasting” rule. It overrides the Section 104 pool whenever you dispose of a token and reacquire the same one within 30 days, which is exactly what an investor does when they sell during a dip and buy back, or try to “crystallise” a loss for tax purposes and re-enter. The result is a gain calculation that often surprises people. This guide explains the rule, the order it is applied in, and the real-world scenarios where it bites. It is an explainer, not tax advice; for your circumstances, consult a qualified UK tax adviser.

What the 30-day rule is — and why it exists

The rule matches a disposal against any acquisition of the same token made in the 30 days following the disposal, in preference to the Section 104 pool. So if you sell 1 BTC today and buy 1 BTC back within the next 30 days, the sale is matched to that rebuy — at the rebuy’s cost — rather than to your pooled average cost.

It exists to stop “bed-and-breakfasting”: the practice of selling an asset purely to realise a gain or loss for tax purposes, then immediately buying it back to keep your position. Without the rule, an investor sitting on a paper loss could sell, claim the loss against other gains, and rebuy seconds later, having changed nothing about their actual holding. The 30-day rule neutralises that by treating the sell-and-rebuy as if the pool was never touched — and it applies whether the outcome helps you or hurts you. It is mechanical, not discretionary.

The matching order

When you dispose of crypto, HMRC matches the disposal against acquisitions in a fixed order before the pool is used:

1. Same-day rule (s.105) — first, against any acquisition of the same token on the same day as the disposal.
2. 30-day rule (s.106A) — then, against acquisitions of the same token in the next 30 days, earliest first.
3. Section 104 pool — only the remainder, after the above, is matched against your pooled average cost.

Most disposals fall straight through to the pool. It is only when you reacquire within the window that the first two rules reshape the numbers — and because they take priority, they can override what you expected the pool to produce.

A worked example — the loss-harvesting trap

This is where the rule most often defeats an investor’s intention. Suppose your BTC pool holds 1 BTC at a £25,000 average cost, the price has fallen, and you want to realise a loss to set against gains elsewhere:

• Day 1: sell 1 BTC for £18,000. You expect a £7,000 loss (£18,000 − £25,000 pooled cost).
• Day 10: buy 1 BTC back for £18,500 — you wanted to keep your position.

Because you reacquired within 30 days, the 30-day rule matches the Day 1 disposal to the Day 10 rebuy, not to the pool. Your gain/loss becomes £18,000 − £18,500 = −£500 — a £500 loss, not the £7,000 you were trying to harvest. The pool is left untouched, still holding 1 BTC at £25,000. The intended tax benefit largely evaporates, because that is precisely what the rule is designed to do. To genuinely realise the larger loss, you would have to stay out of that token for more than 30 days — accepting real market risk, which is the point.

A second example — the rule helping you

The rule is symmetric, so it can also reduce a gain. Suppose your pool average is £10,000 per BTC, the price has risen, and:

• Day 1: sell 1 BTC for £40,000. Against the pool you would expect a £30,000 gain.
• Day 20: buy 1 BTC for £38,000 to re-enter after taking some profit.

The 30-day rule matches the disposal to the Day 20 rebuy: your gain becomes £40,000 − £38,000 = £2,000, not £30,000, and the pool keeps its original 1 BTC at £10,000. The deferred gain has not disappeared — it is baked into the pool for a future disposal — but for this tax year, the rule has shrunk the reportable gain. Neither outcome is something you choose; the rule applies automatically based on your transaction dates.

The same-day rule, and how the two interact

The 30-day rule never works alone — the same-day rule (s.105) sits ahead of it, and understanding the order prevents double-counting. The same-day rule matches a disposal first against any acquisition of the same token on the same calendar day, before the 30-day window is even considered.

A worked example with both in play. Your BTC pool holds 1 BTC at £20,000, and on a single busy day you:

• Buy 1 BTC for £30,000 (morning), then
• Sell 1 BTC for £32,000 (afternoon), then
• Buy 1 BTC for £31,000 eight days later.

The afternoon sale is matched first by the same-day rule to the morning £30,000 purchase — gain £32,000 − £30,000 = £2,000. The same-day match is exhausted by that pairing, so the 30-day rule and the pool are not reached for this disposal; the Day-8 £31,000 buy simply enters the pool, which now holds 2 BTC (the original at £20,000 and the new at £31,000). Had there been no same-day purchase, the sale would have fallen to the 30-day rule and matched the Day-8 rebuy instead. The lesson: the order of matching changes the number, and only software reliably applies it across a real history.

What counts as the “same token”

The rules are per-token, and “same token” means the same virtual digital asset, not merely a similar one. BTC, wrapped BTC (WBTC), and ETH are three different tokens with three different Section 104 pools, and a disposal of one is never matched to an acquisition of another under the same-day or 30-day rules. Each stablecoin is likewise its own pool. This matters because an investor who “sells BTC and buys WBTC” has made a crypto-to-crypto disposal of BTC and an acquisition of a different token — the 30-day rule does not treat them as the same holding, so it does not apply between them, even though the economic exposure is similar.

Why this is hard to track by hand

The difficulty is that the 30-day rule has to be checked for every disposal, against a rolling 30-day forward window, across all of your venues at once — a coin sold on one exchange can be matched to a purchase on another. On a busy history with frequent re-entries, the matching reshuffles gains and losses substantially, and a manual spreadsheet almost always gets some of it wrong. This is one of the core jobs UK crypto-tax software exists to do: Koinly and Recap both apply the same-day and 30-day rules automatically alongside the Section 104 pool. In the CARF reporting era, where HMRC now receives platform data directly, getting this matching right is no longer optional.

Common questions

Does the 30-day rule apply across different exchanges?

Yes. It is token-based, not venue-based. A BTC disposal on one platform can be matched to a BTC acquisition on another within the 30-day window. You must reconcile across all your accounts together.

Does it apply to crypto-to-crypto swaps?

Yes. Acquiring a token via a swap counts as an acquisition for matching, just as disposing of one via a swap counts as a disposal. The rule does not care whether fiat was involved.

Can I avoid the rule by buying a different coin?

Yes — the rule only matches the same token. Selling BTC and buying ETH does not trigger it. But selling BTC and rebuying BTC within 30 days does, regardless of the platform or the amount of fiat in between.

What if I rebuy a smaller amount than I sold?

The rule matches up to the quantity reacquired. If you sell 2 BTC and rebuy 1 BTC within 30 days, 1 BTC of the disposal is matched to the rebuy under s.106A and the other 1 BTC falls to the Section 104 pool.

Does the 30-day rule apply to stablecoins?

Yes — a stablecoin is a virtual digital asset like any other, with its own pool, so selling and rebuying the same stablecoin within 30 days triggers the rule. In practice gains and losses on a stable asset are small, but the matching still applies and still has to be reconciled.

What if I receive staking rewards or an airdrop within the 30 days?

It depends on whether the receipt is an acquisition of the same token. Staking rewards and airdrops are generally income at receipt (at market value) and then enter your pool — and because they are acquisitions of that token, they can be caught by the 30-day matching if they land within the window after a disposal of the same token. This is one of the more counter-intuitive interactions and a strong reason to let software handle the matching rather than eyeball it.

Does CARF change the 30-day rule?

No — CARF is a reporting regime, not a change to the matching rules. But it raises the stakes: HMRC now sees your disposals and reacquisitions directly, so a return that applies the 30-day rule incorrectly is more likely to surface as a mismatch. The rule is the same; the cost of getting it wrong is higher.

The bottom line

The 30-day rule is mechanical, token-based, cross-venue, and applied before the pool — and it routinely produces a different number than an investor expects, especially when they were trying to harvest a loss. Track every disposal against the rolling 30-day window, reconcile across all your venues, and use the current 18%/24% rates against your gains. This guide is general information, not tax advice; for your specific position, consult a qualified UK tax professional or HMRC directly.