Nothing. There is no account, no sign-up, no email address and no identifier of any kind. The calculator does not know who you are and has no mechanism to ask.

The figures you enter are calculated on your own device by an engine that was downloaded to it. They are not transmitted to us, and there is no server that could receive them: TaxMirror has no application server, no database and no account store.

TaxMirror sets no cookies. There are no analytics, no tag manager, no advertising pixels and no third-party scripts of any kind. Because nothing is stored on your device for our purposes, no consent banner is required and none is shown.

If you choose to save a household, it is encrypted with a password you set and the encrypted result is kept in your browser’s local storage (IndexedDB), or in the app’s protected storage on a phone. Only the sealed bytes are stored: never the password, never the key derived from it, and never your figures in readable form.

That storage belongs to you. Nobody else can read it without your password, it is never sent anywhere by us, and clearing your browser data or uninstalling the app removes it. Because we hold nothing, we also cannot recover it for you — which is why the app offers an encrypted export file you can keep yourself.

This is the part that is not zero. To send you the page at all, the server hosting it receives your IP address, the page requested, and details your browser sends such as its type and preferred language. That is inherent to how the web works and is true of every site you visit.

Your preferred language is used once, to send you to the French, Dutch or English version of the page. It is not stored and not recorded against you.

Our server keeps no log of visits. It does record errors, such as a page that failed to load, but those records never contain your IP address: requests reach the server through Cloudflare, so the only address it sees is Cloudflare’s.

The site runs on a server operated by the publisher. Requests reach it through Cloudflare, Inc., which carries the connection, protects the site against attacks and may briefly cache pages. Cloudflare therefore also sees your IP address and the page requested, and handles them as our service provider. Cloudflare is a US company certified under the EU–US Data Privacy Framework.

Tax rules are published as signed static files. When your device fetches them, it verifies the publisher’s signature rather than trusting the infrastructure that served them. Such a request reveals only that a device asked for a rule file, never anything about your household.

TaxMirror is published by Stefan-Lucian Muresan, Vienna, Austria, who is responsible for this site under the GDPR (the controller). For anything about your data, write to [email protected]. Mail to that address is forwarded to the publisher by Cloudflare.

Under the GDPR you have rights of access, rectification, erasure, restriction, objection and portability over personal data held about you. We hold none: the server keeps no log of visits, and everything you enter in the calculator stays on your device. What Cloudflare does with your IP address is set out in Cloudflare’s own privacy policy.

You can complain to a data protection authority. TaxMirror is published from Austria, where that is the Datenschutzbehörde, Barichgasse 40–42, 1030 Vienna. You can also go to the authority where you live, for example the Belgian Data Protection Authority (Autoriteit Gegevensbescherming / Autorité de protection des données), Rue de la Presse 35, 1000 Brussels.

You do not have to take any of this on trust. Load the page, disconnect from the network, and keep using the calculator: it carries on working, because the engine and the rules are already on your device. A tool that sent your figures away could not do that.

Open your browser’s network tab and enter some figures. It stays empty.