You may be planning to sell Bitcoin at a loss before 5 April, then buy it back once the market settles. Warning: a repurchase within 30 days can cause HMRC to rematch the disposal to the new coins, rather than your Section 104 pool. The loss you expected to use against gains may shrink, disappear or move into a different calculation.
Loss harvesting timing strategies need to account for HMRC’s matching order: disposals are matched first with acquisitions on the same day, then acquisitions in the following 30 days, and only then with the Section 104 pool.
Sell before 5 April only after checking 30 days
Selling Bitcoin before 5 April can put a capital loss into the current tax year, but only if the later matching rules do not alter its cost. A tax year runs from 6 April to 5 April, so a disposal on 4 April 2026 falls in 2025/26. A purchase on 10 April can still affect that 4 April calculation.
A disposal is more than cashing out
A disposal is an event that can create a capital gain or capital loss. Selling Bitcoin for pounds is a disposal, but so is swapping Bitcoin for Ether, spending it, or giving it away in most cases. The Taxation of Chargeable Gains Act 1992 applies the capital gains framework to these events.
Your sale time matters, not just the date
HMRC's rules work by calendar day, but reliable records need the transaction time too. Exchanges may export times in UTC while an investor in London reads the trade in British Summer Time. Record the exchange's timestamp, its stated time zone, the GBP value, quantity and fees.
A loss realised on 4 April can offset gains for that tax year, but Bitcoin acquired from 4 April to 4 May may be matched to that sale first. Check planned recurring buys, limit orders and exchange auto-invest settings before you sell.
For UK tax year planning, review potential Bitcoin capital losses well before 5 April rather than treating the final week as the only decision point. A quarterly review can identify realised gains, likely disposals and any purchases that could trigger the same-day matching rule or 30-day bed and breakfast rule. For the year ending 5 April 2026, an online Self Assessment return and any tax due are normally due by 31 January 2027.
Keep UK crypto tax records, including exchange exports and valuation evidence, for at least five years after that filing deadline, so records for 2025/26 should ordinarily be retained until at least 31 January 2032.
A 30-day Bitcoin repurchase can rewrite your loss
Buying Bitcoin within 30 days after a sale can replace the Section 104 cost you expected with the cost of the new purchase. This is the 30-day bed and breakfast rule, a statutory matching order rather than a suggestion from an exchange.
Same-day buys come first
Suppose you buy 0.10 BTC at £70,000 per BTC and sell 0.10 BTC later that day for £67,000. HMRC matches those units first. The result is a £300 loss before allowable fees, not a calculation based on your older pooled Bitcoin.
This is not the US wash-sale rule
Instead, UK rules change the units and acquisition costs matched against the original disposal. A repurchase within the following 30 days may create a gain, a smaller loss, or a larger loss, depending on the new purchase price.
There is an important exception: waiting until day 31 means unmatched units normally fall into the Section 104 pool, which is an average-cost pool for qualifying holdings of that cryptoasset. Day 31 is not a magic tax-saving day, though. A sharp Bitcoin move over 30 or 31 days can cost more than the tax relief sought.
Match the sale date to gains and market exposure
A sensible harvest date matches an expected allowable loss to actual taxable gains, while keeping your investment plan intact. The decision is strongest where gains already exceed the annual exempt amount and the sale does not create unacceptable market exposure.
Use current-year gains before banking losses
If you have realised gains of £12,000 and an allowable Bitcoin loss of £4,000, the loss can reduce the taxable gains to £8,000 before the annual exempt amount is considered. The saving depends on your Capital Gains Tax rate and wider facts.
Losses cannot normally be carried back to an earlier tax year. They can be carried forward after a claim and set against later gains, generally before the annual exempt amount is applied.
Compare four timing choices
This table shows why a sale date alone cannot predict the tax answer. Prices are examples only, and fees should be included in the actual calculation.
| Action | HMRC matching | Tax-year result | Market exposure |
|---|
| Sell 4 April, no buy-back | Usually Section 104 after other checks | Falls in the current tax year | Open-ended |
| Sell 4 April, buy 10 April | 30-day purchase matched first | Falls in current year, cost may change | About 6 days |
| Sell 4 April, buy 6 May | Usually Section 104 pool | Falls in current year | About 32 days |
| Sell 6 April | Same matching sequence applies | Falls in next tax year | Depends on buy-back plan |
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Our recommendation
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A crypto loss harvesting decision should start with the tax position, but it should not end there. Compare realised capital gains that are available to be offset with any allowable capital losses already claimed or expected, then consider spread, fees, market liquidity and the risk of being out of Bitcoin during the repurchase period. A liquid market may make a short sale-and-repurchase plan easier to execute, but volatility can outweigh the value of the tax relief.
If the long-term investment thesis remains unchanged, the key question is whether the expected tax benefit justifies the price risk and the effect of a cryptoasset repurchase within 30 days.
Calculate losses in HMRC's statutory order
HMRC calculates a Bitcoin gain or loss by matching same-day acquisitions first, 30-day acquisitions second, and the Section 104 pool last. An exchange's average-cost display may be useful for monitoring, but it is not proof of the statutory tax result.
A simple before-and-after example
Assume your Section 104 pool holds 1 BTC with an average cost of £50,000. You sell 0.20 BTC on 4 April for £9,000, paying a £20 selling fee. If there is no same-day or following-30-day acquisition, the matched pool cost is £10,000 and the allowable loss is £1,020.
Now buy 0.20 BTC on 12 April for £9,400, with a £20 purchase fee. That new acquisition is matched to the 4 April disposal. The matched cost becomes £9,420, so the loss is £440, not £1,020.
Keep evidence that can be reconciled
Download full CSV or PDF exports before accounts are closed or exchanges alter their history. Retain trade confirmations, wallet addresses, transaction hashes, quantities, timestamps, GBP valuations, deposit and withdrawal reports, and records of fees.
Do not harvest a loss merely because the Bitcoin price is lower. This approach may not fit where there is no taxable disposal, no current or future gain worth preserving the loss for, excessive spread or trading fees, or a sale that conflicts with your investment plan. DeFi activity, corporate holdings, trusts, non-UK residence and large transactions should be checked with a qualified tax adviser before filing.
A tax-year boundary can change when a loss is available even where the Bitcoin price and the Section 104 pool are identical. Assume a taxpayer has £10,000 of realised gains in 2025/26, an available annual exempt amount of £3,000, and sells Bitcoin on 4 April for an allowable current-year loss of £2,000. The loss reduces gains to £8,000, leaving £5,000 taxable after the annual exempt amount. If the same Bitcoin disposal occurs on 6 April instead, the £10,000 gain remains in 2025/26 and the £2,000 loss belongs to 2026/27; it cannot normally be carried back to shelter the earlier-year gain.
Bitcoin acquisition costs, fees and matching rules must still be checked in both cases.
Common questions
Can I sell Bitcoin at a loss and buy it back the next day?
Yes, but HMRC normally matches the sale with that next-day Bitcoin purchase under the 30-day rule. The result may differ sharply from your Section 104 pool calculation, even though the sale remains in the original tax year.
Do I need to report a crypto loss to HMRC?
You should claim an allowable crypto loss if you want to offset gains now or carry it forward. A claim is generally due within four years of the end of the tax year in which the loss arose.
Is moving Bitcoin to my own wallet taxable?
No, moving Bitcoin between wallets you beneficially own is normally not a taxable disposal. Keep both addresses and the transaction hash because an exchange export alone may look like a withdrawal without explaining ownership.
Does the UK have a crypto wash-sale rule?
The UK uses same-day and 30-day matching rules rather than the US wash-sale framework. A repurchase within 30 days changes the acquisition cost matched to your sale rather than following the usual US treatment.
Can a Bitcoin loss reduce future capital gains?
Yes, unused allowable losses can generally be carried forward against later capital gains after a valid claim. They are normally used before the annual exempt amount, which is £3,000 for 2025/26.
Do I declare Bitcoin swaps on Self Assessment?
Yes, swapping Bitcoin for another cryptoasset is usually a disposal for Capital Gains Tax purposes. Record the GBP market value of what you receive at the time of the swap and the fees paid.
The essentials: check the 30 days after every Bitcoin loss sale, not only the 5 April deadline. / Same-day and later purchases can replace your pooled cost with a new purchase cost. / Claim valid losses within four years if you need them for current or future gains. / Preserve exports, wallet evidence, GBP values and fees before preparing Self Assessment.
Related sources
These articles can help you explore the topic in more depth:
