About CryptoTaxCheck — Who We Are and Why We Built It

CryptoTaxCheck is a UK crypto tax calculator and HMRC letter helper. It exists because working out Capital Gains Tax on crypto under HMRC's rules is genuinely hard — same-day matching, the 30-day rule, section 104 pools, a rate change part way through 2024/25 — and because the people who most need help, the tens of thousands who have received an HMRC letter, are often anxious, short of time and wary of uploading years of financial history to a stranger's server.

Who is behind it

Andrew Pickett — founder. Andrew builds and runs CryptoTaxCheck. He designed the product around four principles: apply HMRC's rules exactly as the Cryptoassets Manual describes them and show the working for every disposal; process files in the user's browser so they never leave the device; charge a fair one-off price with no account or subscription; and build for people with back years to sort out, not just the current return.

Qualified reviewer — to be announced. Before launch, the engine's test cases and every guide on this site will be reviewed by a named, qualified UK tax professional (a Chartered Tax Adviser or a member of the ATT, ACCA or ICAEW). Their name, qualification and the date of review will appear here and on each guide under "Reviewed by". Until that review is complete, guides show the "Reviewed by" line as pending.

Why we built it

HMRC sent 81,172 letters, emails and texts to crypto holders in 2025/26, according to Freedom of Information figures reported by the BBC — nearly three times the number two years earlier. Most recipients have not set out to underpay; they are people who did not realise that swapping one coin for another is a disposal, or that the tax-free allowance fell from £12,300 to £3,000 in two years.

GOV.UK says exchange transaction reports "are not tax calculations" and "will not keep track of your pooled costs". That gap — between a CSV of trades and a number you can put on a tax return — is what CryptoTaxCheck fills. It reads your exports, applies the matching rules, and shows you, disposal by disposal, how it got to the answer.

What makes it different

• UK-only and rule-transparent. We do one country's rules and we show them. Every disposal in your results tells you whether it was matched same-day, under the 30-day rule or from the pool, and what the pool looked like before and after.
• Private by design. Your files are parsed in your browser and never uploaded. The only data the calculator sends us is a list of coin symbols and dates when a sterling price is missing.
• No account, no subscription. The estimate is free. A report is a one-off purchase.
• Built for letter recipients. Every tax year from 2019/20 is supported, the 2024/25 mid-year rate change is handled, and the Letter Pack produces a disclosure worksheet for HMRC's Cryptoasset Disclosure Service.

What we are not

We are not tax advisers, and the site is not personal advice. We are independent and not affiliated with, approved by or endorsed by HMRC. Our tool deliberately does not calculate DeFi lending, liquidity pools, NFTs or margin trading; it detects them, flags them and points you to software or an adviser that can help. Our methodology sets out exactly what we do and where the limits are.

How we make money

Two ways: paid reports, and a labelled affiliate relationship with Koinly for users whose needs go beyond our tool. We take no payment from exchanges and run no ads on the calculator or letter pages. Full details are in our affiliate disclosure.

Get in touch

Corrections, questions and feedback are welcome — see the contact page. If you spot an error in a guide, tell us and we will fix it and note the change.