You lost crypto. A project collapsed. An exchange froze withdrawals. You read somewhere that you can write off the loss against your tax bill. Before you file anything, there are three distinctions that almost every DIY guide blurs, and getting them wrong can mean a rejected claim, an enquiry, or a loss that disappears because the window to claim it closed.
This guide works through each scenario in turn, explains what HMRC's Cryptoassets Manual actually says, and tells you where the facts become too specific for a general answer.
The short answer: it depends, and losing keys is not the same as a worthless token
Whether you can claim a tax loss on lost or inaccessible crypto depends entirely on which of three situations applies. Losing private keys or access credentials does not create a capital loss; only a disposal or a negligible value claim can do that. A negligible value claim works only when the asset itself has become worthless, not when it is merely out of reach. Exchange collapse sits in a third category: fact-specific, legally uncertain in places, and never a guaranteed deduction. The table below maps the three scenarios.
| Scenario | Is it a disposal? | Is a loss potentially available? | How |
|---|---|---|---|
| Lost private keys / forgotten password | No | Not unless the asset is also worthless | Negligible value claim if the token itself has collapsed in value; otherwise no loss |
| Rug pull / dead chain (worthless token) | No sale needed | Yes, if the asset is genuinely worthless | Formal negligible value claim (HMRC CRYPTO22500) |
| Exchange collapse (FTX-class) | Fact-specific | Possibly, but no deduction is guaranteed | May be negligible value claim, loss on claim against exchange, or nothing yet; professional judgment required |
Losing private keys: why HMRC does not treat this as a disposal
HMRC's Cryptoassets Manual at CRYPTO22400 is explicit: losing private keys or access to a wallet is not a disposal. No disposal means no CGT event, which means no allowable capital loss.
The asset, from HMRC's perspective, still exists. It remains in your section 104 pool at its original allowable cost. You have not sold it, gifted it, or swapped it. You have simply lost the ability to access it. That is a practical problem, not a tax event.
This matters because many DIY guides and forum posts treat "lost crypto" as interchangeable with "written-off crypto". They are not. If you lost the keys to a wallet containing a token that is still trading at value, you have no loss to claim. The asset is yours; you just cannot reach it.
The only route to a capital loss in a lost-keys situation is if the token itself has also become worthless. In that case, a negligible value claim may be available, but the claim is based on the worthlessness of the asset, not on the loss of access. These are two separate facts, and both must be true for the claim to work.
Genuinely worthless tokens (rug pulls, dead chains): the negligible value claim
HMRC's Cryptoassets Manual at CRYPTO22500 confirms that a negligible value claim is available for cryptoassets that have become genuinely worthless. The claim is a formal election that treats the asset as if it were disposed of at its current negligible value and immediately reacquired at that same negligible value. The result is an allowable capital loss equal to the original acquisition cost, minus the negligible current value (which is typically close to zero).
You do not need to sell the token for the claim to work. This is the mechanism designed for assets that have collapsed to the point where a market sale is impossible or would realise almost nothing.
Common situations where a negligible value claim may be appropriate:
- A rug pull where the development team abandoned the project, liquidity was withdrawn, and the token now trades at a fraction of a penny or not at all.
- A blockchain that has been abandoned, with tokens on it that have no remaining market.
- A token whose smart contract has been exploited and rendered permanently non-functional.
The claim can be backdated to an earlier point in time, provided the asset was already at negligible value on that earlier date. This is practically important: if a rug pull happened in the 2022/23 tax year but you are only now getting your tax affairs in order, you may be able to backdate the claim to the date the token became worthless, provided you can evidence that date.
What counts as "negligible"? HMRC does not fix a precise percentage, but in practice the asset needs to have become substantially worthless, not merely down 80% from its peak. Evidence matters: trading history, blockchain explorer data showing abandoned activity, and project communications are all relevant to supporting the claim.
Negligible value vs lost keys: the distinction DIY guides blur
The clearest way to see the distinction is to work through a paired example.
Suppose you bought 10,000 units of a small-cap token in 2021 for £5,000. In 2023, the project's developers disappeared and the token's value collapsed to effectively zero. You also lost access to the wallet in which you held the tokens because you no longer have the seed phrase.
You have two facts here: the token is worthless, and you cannot access the wallet. Only one of those facts is relevant for the tax claim. The worthlessness of the token is what supports a negligible value claim. The lost seed phrase adds nothing to the claim and does not by itself create a loss.
Now change the scenario. The token still trades at its original value, but you cannot access the wallet. You have no loss to claim. The asset is worth what it was; you simply cannot sell it.
The DIY-guide blur happens because both situations feel like the same outcome to the person experiencing them: the crypto is gone. But HMRC's framework does not care how the situation feels. It cares whether a disposal has occurred or whether a valid negligible value claim can be made. Lost access to a live asset is neither.
Exchange collapse (FTX-class): why it is fact-specific and no deduction is promised
When a major exchange freezes withdrawals and enters administration, the tax position of UK account holders is genuinely uncertain and depends on facts that are not available at the moment of collapse.
HMRC CRYPTO22400 and CRYPTO22500 together point to three possible outcomes, none of which is definite at the point of collapse:
- Negligible value claim on the tokens held at the exchange. If the tokens themselves have become worthless (for example, the exchange held tokens that are now untradeable or the exchange's own token has collapsed), a negligible value claim may be possible. But this depends on whether the token is genuinely worthless, not merely frozen at the exchange.
- Capital loss on the legal claim against the exchange. Account holders in an exchange administration may have a legal claim (a debt or trust claim) against the estate. Whether that claim itself can form the basis of a capital loss, and at what value, is fact-specific, legally complex, and may not be determinable until the administration progresses.
- No crystallised loss yet. If the administration is ongoing and the tokens or claims retain some value, no loss may have crystallised. Filing a loss claim prematurely, before the facts support it, creates risk in an HMRC enquiry.
The honest position is this: exchange collapse situations are not straightforward write-offs. The outcome depends on the specific exchange, the type of assets held, the structure of the administration, and the point in the administration process at which you are filing. Professional advice based on the current facts is the only defensible route.
Filing a loss claim based on a DIY guide written at the time of the collapse, without verifying the current administration status and HMRC's position, is a significant compliance risk.
The step people forget: a capital loss must be CLAIMED to be usable
Even where a capital loss is clearly available, it does not automatically reduce your tax. You must actively claim it in your Self Assessment return.
HMRC's guidance on capital losses confirms that losses must normally be claimed within four years of the end of the tax year in which they arose. A negligible value claim must be made in the Self Assessment return for the year in which the asset became worthless (or backdated to that year, within the same four-year window).
The four-year window is the normal rule. It is not absolute in every circumstance, but it is the deadline to plan around and the one HMRC will apply in the majority of cases.
Practical examples of what this means:
- A rug-pull loss that arose in the 2021/22 tax year (ending 5 April 2022) must normally be claimed by 5 April 2026.
- An exchange collapse that happened in the 2022/23 tax year (ending 5 April 2023) must normally be claimed by 5 April 2027.
- If the tax year has already passed and you have not yet filed a return including the loss, you are using up your window now.
Many people who lost crypto in 2022 or 2023 have not yet claimed the loss. Some assume it happens automatically. Others assumed the situation was too uncertain to file. The window is closing, not waiting.
Carrying losses forward against future gains (why unreported loss years are recoverable value)
Once a capital loss is properly claimed, it can be carried forward indefinitely. There is no expiry date on a reported loss. It offsets future capital gains, including gains from the disposal of other cryptoassets, shares, or other chargeable assets.
This makes unreported loss years significant. If you had a genuine negligible value claim in 2022/23 on a rug-pulled token and you did not file a return for that year, the loss is still potentially recoverable, but you need to file an amended or late return to claim it before the four-year window closes.
The practical value of a carried-forward loss depends on your future gains. For someone who is still actively holding crypto and expects to realise gains in future years, a loss from a collapsed token in 2022 could offset tax at 18% or 24% on future disposals. For a gain of £20,000, a carried-forward loss of £5,000 saves between £900 and £1,200 in tax, depending on your income tax position.
The loss does not carry forward automatically. It must first be claimed. The claim must be made in the correct year's return. That is the threshold requirement that determines whether the value is recovered or permanently lost.
Capital losses are also offset against gains in the same tax year before they are carried forward. You cannot choose to skip the current year to preserve losses for a higher-gain future year; same-year offsetting is mandatory. Losses are applied after the annual exempt amount of £3,000 is used.
Getting a defensible loss position
The situations described in this guide, particularly exchange collapse and negligible value claims on complex tokens, are not ones where a DIY approach is low-risk. HMRC can and does open enquiries into CGT returns, including those claiming losses, and the evidence burden for a negligible value claim on a specific token or an exchange-collapse loss sits with the taxpayer.
A defensible position requires:
- The correct characterisation of the situation (lost keys vs worthless asset vs exchange collapse).
- Evidence that the asset was worthless on the date claimed, including market data, blockchain records, and project-status information.
- The claim filed in the right tax year, within the four-year window.
- Consistency with the rest of your CGT return, including the correct s104 pool calculations for the affected tokens.
If you have unreported losses from collapsed exchanges, rug pulls, or dead chains, the first step is to establish which tax year the loss arose in and whether the four-year window is still open. The CGT planning service covers loss identification and claim preparation for exactly these situations. Where an earlier year is involved and a Self Assessment return needs amending or filing late, the HMRC disclosure service handles the submission process.
If you are unsure which scenario applies to your situation, or whether a claim is even available, the starting point is a conversation about the facts. Losing crypto is painful enough without also losing the tax relief you may legitimately be entitled to, or filing a claim that cannot be defended.