Privacy policy

Version of 2026-11-04

In short

The service does not collect or store your answers. Your tax status is calculated in your browser.

We do not use cookies, advertising identifiers or tracking of individual visitors. For statistics we keep only anonymous daily counters (see below) and use Cloudflare Web Analytics, a cookie-free service.

What data is processed

Your answers (home, family, days of presence, citizenship, etc.) exist only in your browser's memory while the page is open and are not sent to the server.

If you choose to share a link to your result (the “Share” button), your answers are encoded in that link and go to whoever you send it to and to the service you send it through (e-mail, messenger); our server does not receive them, because browsers do not send the part of a link after “#” to the server.

Anonymous counters. To understand how the service is used, our server adds +1 to daily counters: a visit; the country derived from your device's time zone; the domain of the site you came from (for example google.com or chatgpt.com, without the full address); the page viewed; the country selected; the overall result of the check (which country you are resident in, reliability level, whether there is a conflict). No IP address, cookies, identifiers or individual visitor records are stored, so the counters cannot be linked to a person. To avoid counting one visit twice, the browser keeps a flag in tab memory (sessionStorage) that is never sent anywhere and disappears when the tab is closed.

For search engine and AI bots (for example Googlebot or GPTBot) we count requests by the bot name in its user-agent.

Site traffic statistics are also collected by Cloudflare Web Analytics in anonymous form: no cookies, no visitor identifiers and none of your answers.

The hosting provider (Microsoft Azure) may temporarily process technical request data (IP address, browser type) to operate and protect the site under its own policies; the counters are stored in Azure Table Storage.

Feedback form

If you send a message through the form on the Feedback page, we receive the text of the message, the e-mail you provide and the language version of the site. They are delivered as an e-mail to the service operator's mailbox and are used only to read your message and reply to you. They are not stored on the site or in the statistics.

The e-mail is sent via Azure Communication Services (Microsoft). To filter out automated submissions, the form page uses Cloudflare Turnstile (Cloudflare, Inc.), which processes technical data of your browser for this check and does not receive the text of your message. Turnstile is loaded only on the Feedback page.

The legal basis is your consent, which you give by ticking the box in the form; you may withdraw it at any time. We keep the correspondence for no longer than 12 months after the last message. To have it deleted earlier, send a request through the same form from the same e-mail address.

AI assistants (MCP)

You can also run the check through an AI assistant (for example Claude or ChatGPT) if you have connected our MCP server (https://doubletaxation.app/api/mcp) to it yourself. The assistant then sends your answers (home, family, days of presence, citizenship and, if you choose, types and amounts of income) to our server so that the rules engine can compute the result.

The server processes these answers only in memory while handling the request and does not store them — not in a database, not in logs, not in statistics. Statistics only receive +1 to a daily counter of requests with the assistant's name taken from the technical request header (user-agent) — without answers, IP addresses or any identifiers.

What you write to the assistant is processed by its provider (for example Anthropic or OpenAI) under its own terms and privacy policy; we do not receive that data, except the answers the assistant sends to our server for the check.

Sharing with third parties

We do not sell your data or share it with anyone for their own purposes. Technical providers process data only on our behalf and only as described above: Microsoft (website hosting, Azure Table Storage, sending feedback emails), Cloudflare (DNS, Web Analytics, Turnstile, forwarding mail to support@doubletaxation.app) and Google (Google sign-in in the app).

Android mobile app

The DoubleTaxation Android app works without internet access: the rules are built into the app and the check runs on your phone. An account is optional.

Your answers, the result, any profile you save yourself (“Save as my profile”) and your “Days of stay” records (countries and trip dates) are stored only on your phone, encrypted (AES-256, key in Android Keystore). The app does not send them to us or to third parties, shows no ads and does not determine your location: to suggest a country in “Days of stay” it only reads the phone's time zone, on the phone itself. Android backup is disabled for this data.

Anonymous usage statistics: once a day, on the first launch, the app tells our server only that it was opened (and whether this is the first launch after installation), its language, the time zone and the app version — no device or account identifiers, no answers or trips. The server only adds +1 to daily counters and does not store the IP address. You can turn this off in “My profile” → “Settings”.

App lock (the phone’s fingerprint, face or PIN) is turned on by you in “My profile”; biometric data is handled by Android, the app never receives it.

You can delete a saved result with “Delete my profile” in “My profile” or by uninstalling the app — after that it cannot be recovered. “Share” passes a link to the result (it encodes your answers) to the app or person you choose, or copies it. Source links and “Feedback” open in your browser and are covered by the website sections of this policy.

App account and how to delete it

You can sign in to the app with your Google account (“Sign in with Google” in “My profile”); there is no separate password. When you sign in, Google gives us your Google account ID, name and e-mail. We store only these, plus the dates the account was created and last used, in Azure Table Storage (Microsoft), to run your account. Your answers and check results are never sent to the server. We do not share this data with anyone or use it for advertising; it is transferred only over an encrypted connection (HTTPS).

How to delete your account: in the app open “My profile” → “Delete account” → “Yes, delete permanently” and confirm your Google account. The account and all data about it (ID, name, e-mail, dates) are deleted from the server immediately. If you no longer have the app, e-mail support@doubletaxation.app from the address of your Google account — we will delete the data within 30 days and confirm by e-mail.

The account and its data are kept until you delete it. “Sign out” only signs you out on the phone and deletes nothing.

Your rights

To get a copy of your account data, correct it or delete it, e-mail support@doubletaxation.app from the address of your Google account — we will reply within 30 days; you can also delete the account yourself in the app (see the section above). We store no personal data about users of the website and calculator who have no account.