Who is behind this
One person, in the UK, who would rather show you the working.
gains.tax is built and run by Fahad, working in the UK. Not a team page with stock photographs, not a company you cannot find. One person, who wrote the engine, answers [email protected], and sits on the other end of the booking link below.
The tax work behind the engine comes from years spent on UK crypto tax cases, and every rule it applies is published with the statute behind it, so you never have to take that on faith. Read the verification record and judge the engine on its own evidence rather than on a biography.
Why it runs in your browser
Every other UK crypto tax tool works by taking your entire transaction history onto its servers. That is a reasonable engineering choice and a poor deal for you: it creates a database of exactly who holds what, it means somebody else's breach becomes your problem, and it gives the vendor a recurring cost that has to be paid for by a recurring bill.
gains.tax does the arithmetic on your machine instead. Your laptop is more than fast enough. That single decision is why there is nothing to leak, why the free tier can exist at all, and why the price is paid once rather than every April. You can check the claim rather than believe it, open the app, press F12, and watch the network panel stay empty. The security page goes through it properly.
What happens if gains.tax disappears
The fair question to ask about software run by one person, and it has a better answer here than almost anywhere else. Every build of the app is a single self-contained HTML file at a permanent versioned address. Save it to your desktop and it keeps working, offline, with no server to call and no licence to phone home. Your key verifies on your own machine.
So if this site went dark tomorrow, your last download still computes your taxes, and your workspace file is yours on your own disk in a format you can read. That is not a promise about our intentions, it is a property of how the thing is built. Nothing else in this category can say it, because everything else needs its servers to be alive.
How it makes money, plainly
Under 1,000 transactions it is free, with every report, forever, and that is not a trial. Above that a one-time key costs £39 and covers every tax year you have ever had and every one still to come. There is no subscription for tax computation and there never will be, that is a standing rule rather than a launch offer. No investors, no advertising, nobody's data being sold, because there is no data here to sell. The pricing page shows the whole ladder and what the alternatives charge.
If the numbers are ever wrong
Tell me. Email [email protected] with enough detail to reproduce it and it gets fixed and republished promptly, and the verification record grows a test so it cannot come back. That is the actual remedy, and it is worth more than the liability cap in the terms, which exists because every piece of software has one, not because it describes how this is run.
Talk to me first if you want
Twenty-five minutes, video, no sales script. Show me your history and I will tell you honestly whether this handles it, including when the answer is that you want an accountant instead.