5.9 Self Assessment and Crypto: How to Report Your Crypto Tax
Self Assessment and Crypto: How to Report Your Crypto Tax
After this chapter you will understand:
- How crypto fits into the UK Self Assessment system and which form(s) you need to use to report gains and income.
- What basic information HMRC expects from you when you file crypto gains or crypto‑related income.
- How to approach your first crypto‑tax return without panic, using simple steps and, if needed, help from an accountant.
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Why Crypto Still Flows Through Self Assessment
For most UK residents, crypto is not taxed in a special “crypto return”; it flows through the same Self Assessment system that handles income from shares, property, and other investments. If you’re already used to Self Assessment (for rental income, self‑employment, etc.), crypto simply adds another line item. If you’ve never filed before, crypto can be the reason you finally register – and that’s normal and expected.
HMRC looks at crypto gains as Capital Gains Tax events and some crypto income as Income Tax events, so when you file, you’re essentially telling HMRC:
- What your gains and losses were.
- Whether they exceed your CGT allowance.
- If you earned crypto as income (staking, mining, rewards, etc.).
The key lesson is: crypto does not get its own special place in the sky; it lives inside Self Assessment, just like other assets.
Which Forms and Boxes You Need
For typical investors, the main place you tell HMRC about crypto is:
- SA108 – Capital Gains Tax summary pages (within your Self Assessment return).
- SA100 – the main return, where you declare your overall income and confirm that you have capital gains to report.
On the SA108, HMRC expects you to summarise:
- Your total taxable gains for the year from all assets (including crypto).
- Your total allowable losses that you want to set against gains.
- Whether you have used your CGT allowance and how much of it remains.
You do not list every single trade on the form itself; instead you keep detailed records (often generated by your crypto tax software) and use them to calculate your final numbers, which you then summarise on SA108. If you earn crypto as income, that goes on the relevant income pages (e.g., “other income” or “self‑employment income”), depending on the nature of the activity.
How to Approach Your First Crypto‑Tax Return
For beginners, the idea of filing Self Assessment for the first time can feel intimidating, but the process is quite straightforward once you break it down.
Step 1 – Decide if you need to register
If you have exceeded your CGT allowance and owe tax on crypto gains, or you have significant crypto income, you usually need to file Self Assessment. HMRC has online guidance and a simple registration process on GOV.UK; many people register several months before the January 31 deadline just to be safe.
Step 2 – Gather your numbers first
Before you even open the HMRC portal, have your crypto‑tax numbers ready:
- Total gains and losses for the tax year.
- Net gain after losses and CGT allowance.
- GBP estimates of your gains above allowance.
If you’ve used tools like Koinly or an Awaken dashboard, export the report and use it as your raw data.
Step 3 – Fill in the basic return
With your numbers in hand, you can complete the main Self Assessment questions as normal and then navigate to the capital gains section (SA108). Enter your totals there, confirm that you have allowable losses if applicable, and submit the return. HMRC will then calculate your final tax bill based on your income band and the capital gains you report.
Step 4 – Keep a copy and pay by the deadline
Once you file, keep a copy of your return and payment confirmation. HMRC expects payment by 31 January following the tax year, and if you owe tax on crypto, it’s part of that same bill.
When to Get Help from an Accountant
Self Assessment is designed so that many people can file themselves, but crypto adds complexity that some beginners aren’t comfortable with. You should seriously consider professional help if:
- You trade frequently or across many platforms.
- You earn large amounts of crypto income (staking, mining, DeFi rewards).
- You’re unsure whether you’re being treated as an investor or a trader.
- You’re dealing with foreign exchanges, multiple currencies, or complex DeFi structures.
An accountant with crypto tax experience can:
- Review your records and software outputs.
- Help you choose the right boxes on SA108 and the income pages.
- Advise on planning (e.g., staying under the CGT allowance or using losses) without breaking HMRC rules.
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For beginners, it’s often worth paying a small fee upfront to ensure your first crypto tax return is both accurate and HMRC compliant.
By the end of this chapter, you should feel confident that:
- Crypto gains are reported through Self Assessment, not a separate crypto only system.
- You don’t need to list every trade by hand; you summarise them using numbers from your records or tax software.
- You can either complete your self assessment yourself, or hand a clean report of your transactions to an accountant who understands cryptoassets.
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