Crypto capital losses in the UK — claiming and carrying forward
Quick answer: Allowable crypto capital losses can reduce capital gains; claim and retain evidence of unused losses for future years. They do not offset salary. Theft and lost keys are not themselves disposals. A negligible-value claim has separate conditions.
Not every crypto transaction makes money. Losses can reduce your tax bill — but you must claim them correctly and keep evidence.
Calculating a capital loss
Calculate the loss using the allowable cost matched to the disposal, less its proceeds. Apply same-day and 30-day matching before the Section 104 pool; selling below the pooled average does not by itself establish the allowable loss.
Using losses in the tax year
Net losses against net gains. If overall net loss, no CGT due — report the loss on SA108 to preserve carry forward.
Carrying forward
Unused losses roll to future tax years and offset future gains. Keep SA108 submissions as proof.
Lost, stolen or worthless tokens
Theft is not a disposal and does not itself create a CGT loss. Permanently inaccessible tokens and tokens that become worthless require a separate negligible-value assessment. Keep evidence of ownership, acquisition and the loss of value or access.
Use the loss-evidence and negligible-value checklist to distinguish the routes before making a claim.
Tax-loss harvesting caution
Repurchases of the same token within 30 days can change the acquisition cost matched to a disposal. Model the actual transactions and matching sequence before assuming that a sale creates a particular loss.
Review the 30-day matching example before assuming that selling and repurchasing creates the expected loss.
Frequently asked questions
Can I offset crypto losses against salary? +
No. Capital losses offset capital gains only, not Income Tax on employment.