How to report crypto on Self Assessment
Crypto capital gains are reported on the Capital Gains Summary (SA108) pages of your Self Assessment tax return — which now include a dedicated cryptoassets section. You total your disposal proceeds, allowable costs, gains and losses for the tax year, apply the £3,000 annual exempt amount, and pay CGT on the balance at 18% or 24%. You need to file if your gains exceed the allowance, or if you're already in Self Assessment and your total proceeds exceed £50,000. The online filing deadline is 31 January after the tax year ends, and payment is due the same day.
Do you need to file at all?
For a given tax year (6 April to 5 April), you need to report crypto gains if any of these apply:
- Your net gains (after losses) exceed the annual exempt amount — £3,000
- You're already filing a return and your total disposal proceeds exceed £50,000, even if the gains are below the allowance
- You want to claim a capital loss so it's banked for the future (recommended — you have four years to claim)
The steps
- 1. Register for Self Assessment by 5 October after the tax year, if you're not already registered
- 2. Calculate every disposal using the matching rules (same-day → 30-day → Section 104) — this is what our calculator does, with the working shown
- 3. Complete SA108: total proceeds, total allowable costs, gains, losses, and the number of disposals in the cryptoassets section
- 4. Attach or retain your computations — HMRC can ask how you arrived at the figures
- 5. File and pay by 31 January (online). Interest and penalties run from the day after
Losses and prior years
Current-year losses offset current-year gains automatically. Unused losses carry forward indefinitely — but only if claimed, normally within four years of the end of the tax year they arose in. If you booked losses in a crash year and never told HMRC, claiming them now can shelter this year's gains.
There's also an alternative to Self Assessment for simple cases: HMRC's "real time" CGT service lets you report a gain as a one-off without joining Self Assessment. It suits people with a single clean disposal; anything busier belongs on SA108.
Run your own numbers — free
Our calculator applies these rules to your transactions and shows the full working for every disposal — same-day, 30-day and Section 104 matching, per tax year.
Open the calculator →Frequently asked questions
When is the deadline for the 2025/26 tax year?
Online returns and payment: 31 January 2027. Paper returns: 31 October 2026. If you've never filed before, register for Self Assessment by 5 October 2026.
What records must I keep?
Per transaction: date, token, quantity, GBP value, fees, and the type of transaction — plus your pool computations. Keep them at least 5 years after the filing deadline. See our records checklist.
My exchange gave me a statement — is that enough?
It's a start, but exchange statements rarely apply UK matching rules (same-day/30-day/S104) or merge across platforms. You (or your software) still need to compute UK-basis gains.
Sources & methodology
- GOV.UK: Report and pay your Capital Gains Tax
- GOV.UK: Capital Gains Tax allowances (annual exempt amount)
- GOV.UK: Check if you need to pay tax when you sell cryptoassets
Tool v0.2.0 · sources last checked 6 July 2026. This guide is general information, not tax or financial advice — verify your position with a qualified professional before filing.