HMRC’s own worked example refuses to match a repurchase made 31 days after a sale, and matches one made on day 30. That boundary is the easy part of the 30-day rule. The hard part is the assumption sitting underneath it — that this is something which happens to people harvesting losses, and that an ordinary seller can ignore it.
It is not a loss rule. Section 106A of the Taxation of Chargeable Gains Act 1992 is an identification rule and it is mechanical. Sell tokens, then acquire tokens of the same type within the next 30 days in the same capacity, and the disposal is matched to that purchase instead of to your section 104 pool. There is no motive test and no election. It fires on gains exactly as on losses.
Where it sits in the order
CG51555 sets out four steps. A disposal matches first against acquisitions on the same day, then against acquisitions in the 30 days following, then against the section 104 pool, and finally against later acquisitions, earliest first. CRYPTO22200 applies the same sequence to tokens and adds that “each type of token will need its own pool”.
The window runs forward only. Acquisitions before the disposal are simply in the pool, and the day of the sale belongs to the same-day rule. Days one to 30 after the sale are the window, and CG51560’s third example declines to match a purchase landing on day 31.
The rule does not ask why you bought back. It asks when.
What it does to a loss
Take a pool of 10,000 tokens that cost £80,000, an average of £8.00 each. The price has fallen to £5.00. You sell the lot on 10 May 2026 for £50,000, then buy the same 10,000 back on 20 May for £52,000. Prices here are illustrative, not market data.
Because 20 May is day ten, the whole disposal is matched to that repurchase. The cost deducted is the £52,000 you just paid, not the £80,000 in the pool, so the allowable loss is £2,000 and the pool is untouched. Wait until 10 June, which is day 31, and the disposal comes out of the pool instead: the loss is £30,000, the pool empties, and the repurchase starts a fresh pool at £52,000.
The £28,000 of difference is deferred rather than destroyed. It is sitting inside a pool whose cost still reads £80,000 against tokens now worth about £52,000, and it returns on a future disposal. At the 24 per cent rate that is £6,720 of relief postponed; at 18 per cent, £5,040.
It makes gains larger too
Now a pool of 20,000 tokens costing £120,000, £6.00 each. You sell 8,000 on 1 June 2026 at £9.00, for £72,000. The price then falls and on 12 June you buy 3,000 back at £5.00, for £15,000.
Three thousand of the tokens sold are matched to that repurchase and the other 5,000 come out of the pool. The 30-day leg deducts £15,000 against £27,000 of apportioned proceeds; the pool leg deducts £30,000, a quarter of the pool’s cost for a quarter of its units, against £45,000. Total cost £45,000, total gain £27,000.
Had nothing been bought back inside the window, all 8,000 would have come from the pool at £48,000 and the gain would have been £24,000. Buying the dip raised the taxable gain by £3,000, which on an income of £60,000 is £720 of extra capital gains tax on a fortnight in which the token fell.
| One: pool before | 10,000 units, £80,000 |
| Bought back day 10 | Loss £2,000 |
| Bought back day 31 | Loss £30,000 |
| Relief deferred into the pool | £28,000 |
| Two: pool before | 20,000 units, £120,000 |
| Gain, 30-day match | £27,000 |
| Gain, no repurchase | £24,000 |
| Extra CGT at £60,000 income | £720.00 |
| Pool after | 15,000 units, £90,000 |
| Allowance and rates | £3,000; 18% and 24% |
What the rule does not do
It does not stop a disposal being a disposal: the sale happened and it is reportable. It does not touch non-fungible tokens, which CRYPTO22200 says are not pooled at all, and it does not apply to companies, which have a separate ten-day rule running backwards. On the face of section 106A it does not reach a purchase by your spouse either, since the section requires the same person in the same capacity — though HMRC has not said so in terms for cryptoassets.
The obvious response is to wait 31 days, which is mechanically correct and not risk-free. CG13350 points at the anti-avoidance rule in section 16A, which reaches any asset where a main purpose is a tax advantage and can deny a loss outright. It adds that a sale carrying an unconditional agreement to repurchase is not a transfer of beneficial ownership at all, so there is no disposal to match.
Sources, all retrieved 14 September 2026: HMRC Cryptoassets Manual CRYPTO22200 with examples CRYPTO22253 and CRYPTO22255; Capital Gains Manual CG51555, CG51560 and CG13350; TCGA 1992 sections 104 and 106A via legislation.gov.uk; GOV.UK Capital Gains Tax rates and allowances, and Income Tax rates and allowances. Figures used, all 2026/27: annual exempt amount £3,000, CGT 18 and 24 per cent, basic rate band £37,700, personal allowance £12,570. Prices and pool balances are illustrative; every figure was computed for this article. Contested: HMRC publishes nothing on which clock fixes the date of a 24-hour-market disposal for counting the 30 days, nor on whether wrapped or staked tokens match the underlying, and we take no position on either. The spouse point reads section 106A and CG51560; it is not an HMRC statement about cryptoassets. Not a recommendation to buy, sell or hold anything, and not tax advice.