How to Report Cryptocurrency on a UK Self Assessment

Do You Need to Use Self Assessment for Crypto?

You generally need to complete a Self Assessment return if, during the tax year:

• You made capital gains above the annual exempt amount (£3,000 for 2024–25)
• You sold crypto with total proceeds above £50,000, even if your actual profit was £0 or a loss
• You had crypto income (such as staking or rewards)
• You wish to claim allowable capital losses
• You received taxable crypto that must be included in your income

If you only held crypto without disposing of it or receiving income, you may not need to file, but any taxable event usually triggers the requirement. HMRC’s broader position on crypto tax compliance is set out in its guidance on cryptoassets.

The Structure of a Self Assessment Return

Self Assessment returns consist of:

• The main tax return form (SA100) — summarises your overall income and tax position
• Supplementary pages for specific types of income or tax — including SA108 for capital gains

Crypto activity doesn’t have a dedicated main form of its own. Instead:

• Capital gains from crypto are reported via SA108
• Crypto income is reported within the relevant income sections of SA100

The return summarises totals; the detail is shown in supporting documents or attachments.

Reporting Capital Gains from Crypto (SA108)

What SA108 Is

The SA108 form is the Capital Gains Tax summary that you complete alongside your Self Assessment if you have gains (including crypto). It tallies disposals, gains, losses, exemptions and tax due.

New for 2024–25: The "Cryptoassets" Section

HMRC has updated the SA108 form to make crypto reporting more explicit.

Supporting Computations

HMRC’s official notes on completing SA108 explicitly instruct that you send your computations, valuations and any working sheets with the Capital Gains Tax summary pages of your return. They also say do not cross through boxes or write “see attached” in the form itself.

This means:

• The figures you enter on SA108 must be backed by a detailed calculation showing how you arrived at them
• Your workings should include values converted to GBP at the relevant dates, cost bases, and gain/loss computations
• You should attach these workings to the return so HMRC can see them alongside the summary boxes

This requirement is part of HMRC’s procedural instructions for completing the form and aligns with the legal duty to maintain adequate tax records.

What You Report on SA108

On SA108, you typically include:

• Total disposal proceeds from disposals of cryptoassets
• Total allowable costs and purchase costs used for pooling
• Net gains or allowable losses
• Use of annual exempt amount
• Tax due, if any

You do not enter every individual transaction on the form itself. Instead, you supply summary totals on SA108 backed by the attached computations.

Reporting Crypto Income

When Crypto Is Income

Some crypto activities are treated as income rather than capital gains. These include:

• Staking rewards
• Mining or similar rewards
• Crypto received as payment for services
• Airdrops in exchange for activity

The GBP value at the time you receive the crypto must be included in your income. This can be in:

• The miscellaneous income section of SA100
• The self-employment section, if that reflects the nature of the activity
• Employment income sections if you were paid in crypto as part of employment

The income is taxed at your marginal income tax rate (e.g., 20%, 40% or 45%, depending on your total income).

Record Keeping: What HMRC Expects

Good records are essential. HMRC requires that you keep sufficient details to:

• Reconstruct your transactions
• Show how each figure was calculated
• Support your SA108 computations and SA100 income entries

Records should include:

• Transaction dates
• Tokens involved
• GBP values at the time of each event
• Fees and costs
• Wallet addresses and exchange platforms

Need help getting your data? See our guide on Downloading Coinbase CSVs.

Records must generally be kept for at least five years after the January submission deadline for the tax year.

Even if you attach computations to your return, HMRC can still ask for full transaction histories later.

Filing Online vs Paper

In both cases, HMRC’s instruction to include computations alongside SA108 applies.

Common Mistakes When Reporting Crypto

• Reporting totals without supporting calculations
• Forgetting to include swaps or non-GBP disposals
• Mixing income and capital gains figures
• Attaching raw CSVs without explanation
• Writing “see attached” instead of filling the boxes and attaching computations

Clarity and reconciliation between summary figures and attached workings help reduce HMRC follow-ups.