Under UK CGT rules, losing access to Bitcoin or another cryptoasset does not usually create a capital loss. A missing private key, discarded hardware wallet or locked account is normally a loss of access. It is not a disposal.
Can lost bitcoin create a UK capital loss?
Usually, no. A lost private key is normally not a disposal. You have not sold, given away, swapped or otherwise ceased to own the cryptoasset for Capital Gains Tax purposes.
A damaged Ledger device, forgotten password or missing recovery phrase does not usually transfer tokens to anyone else. The crypto remains at its blockchain address. Claiming its original cost as an immediate capital loss is commonly wrong. HMRC does not generally treat an inaccessible wallet as a disposal simply because recovery has failed.
A loss may arise after an actual disposal, qualifying destruction or a valid negligible value claim. That relief concerns the asset's value. It does not concern the owner's inability to access it. A scam transfer may need separate analysis, as crypto may have been sent on-chain to a fraudster. HMRC’s approach is set out in the HMRC Cryptoassets Manual.
Before changing a Self Assessment return: preserve the wallet address and transaction IDs. Keep acquisition records, recovery attempts, device evidence, correspondence and dated market prices. A claim supported by records is easier to explain than one built from memory years later.
Why a missing key is not a disposal
The blockchain may still show the asset. This can be true even when the holder can no longer move it.
A CGT calculation normally needs proceeds from a disposal. It can also need a rule that treats you as having disposed of an asset. Losing a seed phrase does neither. It stops you signing a transaction, but does not itself remove ownership or value.
Ownership, value and blockchain evidence
A wallet recovery phrase can recreate the private keys that control a wallet. Its loss may be permanent. Bitcoin can remain visible and retain a quoted market value. An asset with an observable market value is unlikely to qualify for negligible value relief merely because its owner cannot access it. Wallet addresses, withdrawal records and recovery evidence may support ownership. They do not prove a disposal.
Four events HMRC treats differently
| What happened? | Likely CGT position | Useful evidence |
|---|
| Private key or seed phrase lost | Usually no disposal | Wallet address, recovery logs, purchase records |
| Token genuinely becomes negligible | A section 24(2) claim may be possible | Market evidence and dates showing near-zero value |
| Crypto sent to a scammer | Depends on facts and HMRC treatment | Transaction ID, police or Action Fraud report, messages |
| Token destroyed or ceased to exist | May create a distinct loss position | Protocol records, project notices, valuations |
Before treating a lost Bitcoin private key as permanently inaccessible, make and record proportionate recovery attempts. Do the same for a forgotten crypto wallet password. Check password managers, encrypted backups, old devices, cloud storage and written records. Check whether a missing recovery phrase exists elsewhere.
Document a hardware wallet loss separately from the loss of its seed phrase. The device alone does not prove that access is beyond recovery.
Keep dated wallet recovery records and blockchain address evidence. Keep exchange withdrawal confirmations and acquisition records that link the address to the taxpayer. These records help show ownership. They also show whether the event was loss of access, a cryptoasset disposal or a crypto scam transfer.
Choose the right relief and calculate it
Identify the event first. Then calculate the tax result.
A negligible value claim under section 24(2) TCGA 1992 treats an asset as disposed of and reacquired for nil proceeds. It may create an allowable loss when the asset has genuinely become negligible in value. It is not relief for lost passwords. Do not claim solely because a missing key blocks access to Bitcoin with a quoted market value.
Negligible value claims in practice
The test concerns the token, not the holder’s access. An abandoned token with no realistic market may qualify. It must also have no real prospect of value. Actively traded Bitcoin will rarely qualify. The claim creates a deemed disposal and reacquisition at nil proceeds. This makes dated valuation evidence important.
Section 104 pool calculation example
Cryptoassets of the same type are generally pooled under the Section 104 pool. Average pooled cost normally applies, rather than the cost of a chosen purchase. Suppose 0.60 BTC has pooled allowable cost of £14,000. A qualifying nil-proceeds event affects 0.20 BTC. The calculation would start with about £4,667 of pooled cost. Same-day and 30-day matching rules can change this result.
| Check before a loss claim | Why it changes the result |
|---|
| Same-day acquisitions | They are matched before the Section 104 pool. |
| Purchases in the next 30 days | They may be matched before pooled holdings. |
| Exchange-to-wallet transfers | They help reconcile ownership, but are usually not disposals. |
Destruction, theft and scam losses
Destruction concerns the cryptoasset. It does not merely concern the device that holds its keys. A discarded hardware wallet does not prove that Bitcoin was destroyed. Scam transfers, exchange failures, hacks and inaccessible wallets need different factual and CGT analysis. From 1 January 2026, reconcile exchange reports, wallet movements and tax records carefully.
This guidance is not relevant where access has been restored. It also does not apply where the crypto was sold or swapped normally. It may not apply if a company held the crypto or if you are outside the UK CGT regime. It cannot decide disputed facts or guarantee HMRC will accept a claim. High-value cases, theft and scams need tailored professional advice before you submit or amend a return.
A worked example shows why the deemed reacquisition matters. Assume a taxpayer’s Section 104 pool contains 0.60 BTC. Its allowable pooled cost is £14,000. Assume there are no same-day or 30-day acquisitions to match.
Suppose 0.20 BTC qualifies for a negligible value claim. The amount specified in the claim is nil. The attributable pooled cost is £4,666.67 (£14,000 × 0.20 ÷ 0.60). Nil proceeds produce an initial allowable capital loss of £4,666.67.
The 0.20 BTC is also treated as reacquired for nil. It remains in the pool at a nil base cost. The pool then contains 0.60 BTC. Its total allowable cost is £9,333.33.
This is relief for an asset with negligible value. It is not relief for inaccessible Bitcoin that still has a market value.
The UK Cryptoasset Reporting Framework has practical effects from 1 January 2026. UK reporting cryptoasset service providers must collect specified customer, tax-residence and transaction information. They must report to HMRC through the relevant annual reporting cycle. Exchange data may then be compared more readily with a taxpayer’s Self Assessment return. It will not necessarily show every self-custodied wallet. It also cannot prove that a wallet holder lost a key.
Reconcile exchange statements with deposits, withdrawals, wallet addresses and transaction IDs. Keep an explanation for transfers between wallets you control. A missing record does not prove a disposal. An unexplained on-chain transfer may still need a clear factual explanation.
Frequently asked questions
Can I claim a capital loss for lost bitcoin?
You cannot usually claim a loss merely because access was lost. You need a disposal, valid deemed disposal or another qualifying event.
Can inaccessible crypto qualify as negligible?
Not merely because it cannot be moved. The token itself must have become negligible in value.
What records should I keep for HMRC?
Keep wallet addresses, transaction IDs, exchange statements and purchase records. Keep recovery logs, dated valuations and scam or device-loss evidence.
When should I report a crypto loss to HMRC?
Report an allowable loss through Self Assessment for the relevant tax year. Do this only after checking the legal basis and Section 104 calculation.
The essentials:- A lost key usually blocks access, but does not itself create a CGT disposal.
- Negligible value relief tests the token’s value, not the value of a lost recovery phrase.
- Use the Section 104 pool and matching rules. Do not use the cost of one chosen purchase.
- Keep on-chain, device and exchange evidence before submitting or amending Self Assessment.
Related sources
These articles can help you explore the topic in more depth:
