On 3 April, your portfolio is down £8,000 on a token you still believe in, while earlier trades have already produced £5,000 of taxable gains. Selling before the tax year closes may reduce the bill, but a quick rebuy can change the expected loss calculation.
When to realise losses for UK tax relief: you normally need a taxable disposal—selling, swapping or spending—before 5 April; a paper loss does not qualify. Compare realised gains, losses and the £3,000 Annual Exempt Amount, then check matching rules before rebuying.
Compare gains before selling before 5 April
Compare completed gains and losses before deciding whether to sell. The UK tax year runs from 6 April to 5 April, so disposals on either side of that date fall into different tax years.
Separate paper losses from disposals
Count only completed disposals in your calculation. Moving tokens between wallets you control is not normally a disposal, but selling, swapping or spending tokens can create a gain or loss in GBP.
Test the tax-year benefit
For the tax year ending 5 April 2026, compare your gains after losses with the £3,000 Annual Exempt Amount. A loss is not wasted merely because it is unused this year, provided it is claimed or notified to HMRC within the deadline.
Decide whether waiting is sensible
Consider whether the expected tax benefit justifies selling now rather than waiting. The timing decision should take account of your existing gains, the likely loss after matching rules and your investment plans.
Sell now only if your gains need the loss
Sell before 5 April only if the disposal produces a useful loss after matching rules. This is clearest where gains already exceed the annual allowance and you can avoid buying the same token for 30 days.
Use the same-year offset first
Offset allowable losses against chargeable gains in the same tax year. A capital loss reduces capital gains, not salary, bank interest, PAYE Income Tax or National Insurance.
Carry forward what remains
Carry forward unused allowable losses against future chargeable gains. They can reduce later gains on cryptoassets, shares, funds or property if claimed or notified to HMRC in time.
Before-5-April loss decision path
1. Check
List completed gains in GBP
2. Dispose
Sell, swap or spend before 5 April
3. Wait
Avoid same-token buys for 30 days
4. Claim
Report or notify HMRC by deadline
A numerical comparison can make the timing decision clearer. Suppose that, in the tax year ending 5 April 2026, you have £8,000 of chargeable gains from earlier cryptoasset disposals and realise £5,000 of allowable capital losses before 5 April. Your net gain is then £3,000, so the £3,000 Annual Exempt Amount leaves no crypto capital gains tax to pay, assuming no other capital gains or losses. If instead you have £5,000 of gains and realise £8,000 of losses, you may be able to claim only enough loss to reduce the year’s gains to the exempt amount and carry forward the balance, rather than unnecessarily using losses against gains already covered by the allowance.
The exact claim position should be checked before filing.
Avoid a 30-day rebuy calculation trap
Check purchases of the same token for 30 days after a sale. HMRC generally matches disposals first to same-day acquisitions, then acquisitions in the following 30 days, then the Section 104 pool.
Apply same-day and 30-day matching
Match same-day purchases before older holdings, then match purchases within 30 days. A rebuy can replace the pooled cost you expected to use and substantially reduce or alter the apparent loss.
| Action | HMRC order | Likely result |
|---|
| Sell and buy the same day | Same-day rule | New purchase sets the matched cost |
| Sell, then rebuy within 30 days | 30-day rule | Expected pool loss may shrink or change |
| Sell and wait over 30 days | Section 104 holding rules | Pooled average cost usually applies |
Check the Section 104 pool last
Use the Section 104 pool only after same-day and 30-day matches are removed. The pool combines the allowable cost and quantity of identical tokens held.
For example, assume you sell 1 ETH on 20 March for £1,200 and expect to calculate the disposal against a £2,000-per-ETH cost in your Section 104 pool, producing an £800 loss. If you buy 1 ETH again on 5 April for £1,150, the 30-day matching rule normally matches the 20 March disposal to that later acquisition instead of the pool. Ignoring allowable fees, the calculated loss becomes £50, not £800.
A same-day matching purchase takes priority even over the 30-day rule. This is why a same-token rebuy should be checked across every exchange and wallet before relying on an apparent tax loss.
File the loss and keep HMRC evidence
Claim or notify the loss before the four-year deadline expires. For a loss arising in the tax year ended 5 April 2026, the usual deadline is 5 April 2030.
Build your evidence file now
Save transaction records while exchange data remains available. Keep exchange exports, wallet addresses, transaction hashes, fees and GBP valuations for every acquisition and disposal.
Treat missing or worthless tokens differently
Do not treat stolen, lost or frozen tokens as an ordinary sale. Worthless assets, hacks and insolvent exchanges may require a negligible value claim or another specific analysis.
⚠️ Do not wait until a future profitable year to find old records. Some exchange exports become unavailable after account closure or platform changes.
For HMRC crypto tax reporting, record the loss in the Capital Gains pages of your Self Assessment return if you already submit one. For the tax year ending 5 April 2026, an online Self Assessment return is normally due by 31 January 2027. If you do not normally file a return, or need to preserve a loss without otherwise completing Self Assessment, a loss can generally be notified or claimed directly with HMRC, subject to the four-year time limit.
Keep a calculation showing acquisition cost, allowable fees, GBP disposal proceeds, matching-rule adjustments and the resulting loss. A transaction export alone may not show the Section 104 calculation needed to support the claim.
FAQs
Can I claim a crypto loss without selling?
No, a price fall alone does not create an allowable UK capital loss. You normally need a taxable disposal, unless a valid negligible value claim applies to a genuinely worthless asset.
Do I have to pay capital gains tax on crypto?
You may pay Capital Gains Tax when a crypto disposal creates net gains above your available allowance. Selling for GBP, swapping tokens, spending crypto and certain gifts can all be disposals.
What is the 30-day rule for crypto in the UK?
HMRC generally matches a sale with acquisitions of the same token made in the following 30 days. This can change the loss calculation before the Section 104 pool is considered.
Can crypto losses reduce my salary tax bill?
No, allowable crypto losses reduce chargeable capital gains rather than employment income. They cannot normally reduce PAYE Income Tax or National Insurance.
How long do I have to report a crypto loss?
You usually have four years from the end of the tax year in which the loss arose. A loss from the year ended 5 April 2026 generally needs notification or a claim by 5 April 2030.
Can I carry crypto losses forward in the UK?
Yes, unused allowable losses can be carried forward against future chargeable gains after they are properly claimed. They may offset gains on crypto, shares or other chargeable assets.
Does moving crypto to my own wallet create a loss?
No, moving tokens between wallets you control is not normally a disposal. Keep the transaction hash because it helps prove that ownership did not change.
The essential points:- Sell before 5 April only after comparing actual gains, losses and the £3,000 annual allowance.
- A paper loss becomes relevant only after a qualifying disposal or a valid special claim.
- Check same-day and 30-day purchases before relying on a Section 104 pool loss.
- Keep GBP calculations and evidence, then claim or notify HMRC within four years.
Related sources
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