Filing crypto on your self assessment return requires the right boxes and calculations. Here’s where everything goes.
Do You Need to File?
| Condition | Must File? |
|---|
| Crypto gains over £3,000 | Yes |
| Total disposals over £50,000 | Yes (even if gain is under £3K) |
| Crypto income over £1,000 | Yes |
| Already file self assessment | Yes (add crypto sections) |
| Gains under £3K and disposals under £50K and no other filing requirement | No |
Where to Report Capital Gains
SA108 (Capital Gains Tax) Pages
| Box | What to Enter |
|---|
| Box 7 | Total chargeable gains from crypto |
| Box 8 | Total allowable losses from crypto |
| Box 9 | Unused losses from previous years |
| Box 10 | Net chargeable gains (Box 7 - Box 8 - Box 9) |
| Box 35 | Annual exempt amount (£3,000 for 2025-26) |
| Box 36 | Taxable gain (Box 10 - Box 35) |
Where to Report Crypto Income
| Income Type | Section | Box |
|---|
| Staking rewards (occasional) | SA100 (Main return) | Box 9 (Miscellaneous income) |
| Staking rewards (trading) | SA103 (Self-employment) | Trading income |
| Mining income (hobby) | SA100 | Box 9 |
| Mining income (business) | SA103 | Trading income |
| Airdrops (occasional) | SA100 | Box 9 |
| Airdrops (trading) | SA103 | Trading income |
| DeFi lending interest | SA100 | Box 9 |
Self-Employment vs Miscellaneous Income
| Factor | Miscellaneous (Box 9) | Self-Employment (SA103) |
|---|
| Frequency | Occasional | Regular, organised |
| Profit motive | Incidental | Primary activity |
| Hobby or business | Hobby | Business |
| Expenses | Not deductible | Deductible |
| National Insurance | No | Yes |
| Situation | Best Approach |
|---|
| Missing transaction data | Use best estimate, note the method |
| Lost exchange access | Reconstruct from blockchain data |
| Incomplete wallet records | Document what you have |
| Complex DeFi interactions | Use crypto tax software |
HMRC accepts reasonable estimates if exact figures are unavailable, but exact records are better.
Penalties for Errors
| Error Type | Penalty |
|---|
| Careless error | 0-30% of tax due |
| Deliberate error | 20-70% of tax due |
| Deliberate + concealed | 30-100% of tax due |
| Late filing | £100 + daily penalties |
Deadline
| Event | Date |
|---|
| Tax year ends | 5 April 2026 |
| Online return deadline | 31 January 2027 |
| Payment deadline | 31 January 2027 |
Bottom Line
Report crypto capital gains on SA108 (CGT pages). Report crypto income (staking, mining, airdrops) on SA100 Box 9 (miscellaneous) or SA103 (if trading as a business). Use crypto tax software for accuracy. File by 31 January. If you’re unsure about any section, professional advice is worth the cost to avoid penalties.
This content is for educational purposes only. Not financial advice. Do your own research before investing.