¿Te preocupa cómo declarar pérdidas en Bitcoin y otras criptomonedas ante HMRC? ¿No sabe cómo las pérdidas influyen en la factura del Capital Gains Tax (CGT) o qué pruebas reunir para reclamar? Esta guía ofrece pasos claros, ejemplos numéricos y plantillas prácticas centradas exclusivamente en crypto loss relief para individuos residentes en England.
En pocos minutos se describen los efectos sobre CGT, cómo reclamar pérdidas admisibles en disposals de Bitcoin, las reglas de same‑day y 30‑day matching, cómo compensar con otras ganancias y qué registros conservar para sostener una reclamación válida ante HMRC.
Key takeaways: what to know in 1 minute
- Crypto loss relief reduces taxable capital gains, not income tax: allowable losses from disposals of cryptoassets can be set against capital gains in the same tax year or carried forward.
- Claim losses promptly: a claim to set allowable losses against gains must be made on the Self Assessment (SA108) or by written notice if no return is required; timely reporting preserves relief.
- Same‑day and 30‑day rules apply: disposals that match acquisitions on the same day or within 30 days may change which gain or loss is recognised — important for loss harvesting.
- Keep granular records: transaction date/time, description, counterparty, value in GBP at disposal/acquisition, and wallet/exchange evidence; HMRC expects a verifiable audit trail.
- Losses from theft or scams may be complex: some losses can be allowable if they meet disposal definitions and evidence thresholds; consider specialist advice.
How crypto loss relief affects capital gains tax
Crypto loss relief operates within the capital gains regime: when a disposal of a cryptoasset results in a loss, that loss can reduce taxable capital gains for the same tax year or be carried forward to offset future gains. The process follows the usual CGT rules with crypto treated as a chargeable asset for most private individuals under HMRC guidance.
Key consequences:
- A recognised allowable loss reduces the pool of gains subject to CGT, lowering the net gain after the annual exempt amount.
- If losses exceed gains in a tax year, the excess can be carried forward and used against later gains, provided the loss is reported to HMRC in the relevant tax year.
- Losses do not create an income tax deduction for most personal disposals; they apply only to capital gains unless a trading income case can be proven.
Relevant HMRC source: HMRC: Tax on cryptoassets.
Claiming allowable losses on Bitcoin disposals
A disposal creates a loss when the amount received (or the market value if exchanged for another asset) is less than the allowable cost basis. The calculation steps:
- Establish the disposal proceeds in GBP at the disposal time (use spot rate at the moment of disposal).
- Determine the allowable cost: acquisition cost plus incidental costs (exchange fees, network fees attributable to acquisition/disposal).
- Apply the matching rules (same‑day, 30‑day, and Section 104 pooling) to assign which acquisition is matched to the disposal.
- Compute gain or loss: disposal proceeds minus allowable cost for the matched units.
Practical example (single wallet to fiat sale):
- Bought 0.5 BTC at £20,000 (total cost £10,000) including fees.
- Sold 0.5 BTC later for £7,500 (after fees).
- Resulting allowable loss = £7,500 − £10,000 = £2,500 loss.
If matching rules reassign a different cost basis (for example, using earlier pooled holdings), the computed loss may vary; therefore, apply matching rules carefully.
Offsetting crypto losses against other gains
Allowable losses from crypto disposals offset chargeable gains in this order:
- First, gains of the same tax year are reduced.
- If losses remain, they can be carried forward to offset gains in subsequent tax years.
Losses cannot usually be set against income tax liabilities for personal investors. However, if HMRC determines an individual is trading in crypto as a business, different rules apply and losses may affect income tax. Distinguish investor behaviour from trading (frequency, organisation, businesslike intent).
Table: how losses can be used (comparative)
| Scenario |
Can crypto loss relief apply? |
Practical note |
| Reduce gains in same tax year |
Yes |
Report on SA108 to claim relief |
| Carry forward unused losses |
Yes |
Must report loss in year incurred to preserve carry‑forward |
| Offset against income tax (investor) |
No |
Only applies for trading cases; evidence required |
Same‑day, 30‑day matching and crypto disposals
Matching rules determine which acquisition cost pairs with a disposal. For crypto, HMRC applies the same principles used for other intangible assets:
- Same‑day rule: acquisitions made on the same day as a disposal are matched first.
- 30‑day rule (bed and breakfast rule): acquisitions within 30 days after a disposal are matched next.
- Section 104 pooling: any remaining holdings of the same asset are pooled and matched on a first‑in pooled basis.
Example showing why it matters for loss relief:
- Bought 1 BTC on 1 Jan at £30,000; bought 0.2 BTC on 10 Mar at £10,000; sold 0.2 BTC on 10 Mar at £6,000.
- Same‑day matching will pair the sale with the 10 Mar acquisition (cost £10,000) producing a £4,000 loss. If same‑day acquisition did not exist, pooling could allocate a different cost basis and change the loss amount.
Practical tips:
- When planning loss harvesting, be aware that buying back within 30 days may force an unfavourable match.
- Use timed reconstructions of exchange/wallet timestamps to substantiate matches.
Reporting crypto losses to HMRC in self‑assessment
Reporting steps for individuals who submit Self Assessment:
- Complete the CGT section of the Self Assessment form and attach SA108 where required. Use the figure for net gains after applying allowable losses.
- Enter details of disposals and losses in the supplementary pages or keep detailed calculations in case HMRC requests evidence.
- If no Self Assessment is required, a written claim to HMRC to accept a loss for carry‑forward is still required within the tax year.
Useful HMRC resources:
- SA108 guidance and forms: HMRC Self Assessment forms
- Tax on cryptoassets collection: HMRC: Tax on cryptoassets
Common reporting errors to avoid:
- Failing to convert values to GBP using an appropriate rate at disposal time.
- Omitting network and exchange costs from the allowable cost.
- Not applying same‑day/30‑day matching correctly.
Records to keep for crypto loss relief claims
HMRC expects a clear audit trail. Maintain the following items for each disposal and acquisition:
- Date and time of each transaction (UTC recommended).
- Description of asset (e.g. BTC), quantity and unique identifiers where available (transaction hash).
- Counterparty or exchange details and wallet addresses.
- Consideration received or paid in GBP (with source of exchange rate).
- Any fees or commissions with explanation of allocation.
- Screenshots or CSV exports from exchanges and wallet logs.
Retention period: keep records for at least five years after the 31 January submission deadline of the relevant tax year.
Checklist to present to HMRC on request:
- CSV ledger with timestamped transactions and GBP conversions.
- Exchange withdrawal/deposit proofs linking on‑chain transfers.
- Bank statements showing fiat receipts.
Claim process at a glance
Crypto loss relief: Claim process in 5 steps
1️⃣
Gather transaction recordsExport CSV from exchanges & wallet transactions
2️⃣
Apply matching rulesSame‑day → 30‑day → pooling
3️⃣
Calculate loss in GBPInclude fees and use spot rates
4️⃣
Report on SA108Enter net gains and attach calculations
5️⃣
Retain recordsKeep evidence for 5+ years
Advantages, risks and common mistakes
Benefits / when to apply ✅
- Reduces CGT bill for investors with net gains.
- Carries forward when losses exceed gains, preserving future relief.
- Useful for tax planning when aligning disposals to reduce taxable gains.
Errors to avoid / risks ⚠️
- Misapplying same‑day/30‑day rules and losing intended loss relief.
- Poor recordkeeping leading HMRC to disallow relief.
- Treating trading activity as simple investment without assessing tax status; trading classification can change treatment of losses.
Frequently asked questions
What is crypto loss relief and how does it work?
Crypto loss relief means using an allowable capital loss from a crypto disposal to reduce taxable capital gains in the same year or future years. The loss is the shortfall between proceeds and allowable cost.
Can losses from hacked wallets be claimed?
Potentially, but HMRC requires evidence that a disposal occurred and proof of theft. These claims are fact‑sensitive and should be supported by police reports, exchange records and forensic traces.
How does one report a loss if not required to file Self Assessment?
Submit a written claim to HMRC within the tax year stating the amount and basis of the loss; alternatively, register for Self Assessment and report using SA108.
Do same‑day and 30‑day matching rules apply to decentralised exchange trades?
Yes. Matching rules apply regardless of venue; timestamps and transaction hashes can prove timings. Ensure records capture exact times in UTC.
Can losses be set against income tax?
Not usually for investors. If HMRC determines that cryptoactivity amounts to trading, different rules apply and losses may affect income tax. Professional advice is recommended.
How long should transaction records be kept?
At least five years from the 31 January following the tax year in which the transaction was reported.
What exchange rate should be used to convert crypto to GBP?
Use a reliable market spot rate at the moment of disposal; record the source and timestamp (for example, Coinbase spot rate at 14:03 UTC).
What if HMRC queries a loss claim?
Provide the transactional ledger, exchange exports, bank receipts and correspondence. If uncertain, seek an independent tax adviser or consult an accountant experienced in crypto taxation.
- Export a complete CSV ledger from all exchanges and wallets for the tax year, including timestamps and GBP values.
- Reconstruct matching using same‑day and 30‑day rules to identify allowable losses and document calculations.
- File Self Assessment (SA108) or submit a written claim to HMRC within the tax year to secure carry‑forward rights.