What gains.tax is and what it never does
Checked against app build 2026-08-26-01-41 on 2026-08-26.
What is gains.tax?
gains.tax is a UK crypto tax calculator that runs entirely in your browser. You open the app, you bring your transaction history to it, and every calculation happens on your machine. There is no server holding a copy of your financial life, because nothing is ever sent to one. You can verify this yourself, open the browser’s network panel while you work and watch the silence.
What does the app actually do with my history?
It imports, reconciles, applies the UK matching rules, and produces reports that show their working.
History comes in from exchange exports and other tax tools, and is reconciled against the row count shown on screen. The engine then applies the UK matching rules, section 104 pooling, same-day matching, and the 30-day rule, and produces reports where every disposal names the rule and the legislation behind it. The rules themselves are published with their proofs on the verification page. If you only want a figure for a handful of trades rather than a whole history, the capital gains tax calculator and the crypto profit calculator run without an import at all.
What will gains.tax never do?
Four things, and the list is standing, not aspirational.
Never uploads your data. The optional exceptions, wallet scanning, price lookups, and exchange sync, are visible before they happen and explained in the privacy model.
Never requires a signup. There is no account, no password, and no profile.
Never charges per tax year. The app is free under 1,000 transactions, reports included. Past that, one payment covers every tax year you have ever had and every one still to come.
Never holds your data hostage. Your session file exports at any size, paid or not, always.
What does it cost?
Nothing under 1,000 transactions.
Above that, report downloads ask for a licence key, priced on the pricing page, one payment, no subscription. Everything else keeps working without one, importing, reconciling, the dashboard, and the session export.