Your tax data online: 6 questions for any provider (2026)

Six questions decide whether a provider deserves your salary certificate, your bank statements and your pillar 3a statement. In which country are your documents processed and stored? Is an AI model trained on them? How quickly is your data really gone after deletion, backups included? Who is legally responsible, and under which law? Which other companies are involved? And what can you demand if you want to know exactly? Each of those has a checkable answer, and it belongs on a public page with a country, a company name and a date attached to it. The word "secure" on a home page is not one of those answers, because every provider writes it.

The folder you hand over the counter

At a copy shop you hand a folder across the counter. Whether copies get made isn't the interesting part, that's why you walked in. What you'd actually want to know is whether the folder stays in the shop or travels to another country, whether someone in the back room gets to read along, whether a copy ends up in an archive you've never seen, and when exactly the whole thing gets shredded.

Tax paperwork raises the stakes considerably. Salary, wealth, debts, family situation, health insurance: that's a household's complete financial biography sitting in one stack.

Six minutes on six questions before you upload it is a fair trade.

Question 1: In which country are my documents processed and stored?

A solid answer names the country, the hosting partner, and any processing step that leaves the country. "Your data is safe with us" and "encrypted transmission" don't answer it, because neither says anything about where the data sits afterwards. There's a related mix-up worth knowing about: a provider can be a Swiss company and still have the processing done abroad. Company seat and processing location are two different things, and only the second decides whose authorities could in theory demand access.

At TaxWize: All tax documents and the data extracted from them sit on Swiss infrastructure, hosted by Infomaniak in Swiss data centres. I set it up that way on purpose when I built the thing. One step involving your payment data leaves Switzerland and is disclosed as an exception: payment processing via Stripe, which may process data in the EU and the United States. Stripe never receives your tax documents or the tax data extracted from them. Details on the data-protection page, and which component runs on which machine is in where your tax data actually runs.

Question 2: Who reads along, and is an AI model trained on it?

More and more tax tools use AI to read documents, so the honest question isn't whether a provider uses AI. It's whose model it is, where it runs, and what happens to what it reads. With internationally operated AI assistants the answer depends heavily on the plan you're on, and I've collected the sourced detail on the comparison page TaxWize and ChatGPT.

At TaxWize: The language model that reads your documents is hosted by Infomaniak in Switzerland. Text recognition for scanned pages runs self-hosted on that same Swiss infrastructure, so no further service provider reads your documents. Your content is not used to train AI models. AI output can be incomplete or wrong, which is why TaxWize shows you the extracted values for checking before they get used. What runs after that is a deterministic rule set built on your canton's published tariffs. Reading the documents is the AI step, and that is the step you can check.

Question 3: How quickly is my data really gone after deletion?

"You can delete your data at any time" is half an answer, because every seriously operated platform runs nightly backups. A good answer states both moments separately: when the data leaves the live systems, and when it's gone from the backups.

At TaxWize: Deleting your data in the settings removes declarations, tax calculations, extracted values, uploaded documents and recorded assets from the live systems immediately. Backups still holding that data are cleared within 30 days. Data deletion keeps your login so you can start fresh, account deletion also removes the login identity and can't be undone. Set out on the security page.

Question 4: Who is legally responsible, and which law applies?

A serious provider names the full company name, the legal form, the seat and the Swiss UID, so you can look it up in the commercial register yourself. Without that, you don't know who you're dealing with when something goes wrong.

At TaxWize: The service is operated by Szakács Solutions, a sole proprietorship in the canton of Aargau, Swiss UID CHE-289.567.114, entered in the commercial register of the canton of Aargau; the registered office and address are in the register extract and in the imprint. Swiss data protection law (DSG) applies, and my own name is on the register entry.

Question 5: Which other companies are involved?

No provider does everything itself. What matters is how many processors there are, where they sit and what each of them handles. A short, complete list with locations beats no list at all, and payment processing is usually the entry worth reading twice.

At TaxWize: Four entries in the register: two external processors under a data-processing agreement, plus two components I run myself. The external ones are Infomaniak (Switzerland) for hosting, AI-assisted document processing and email, and Stripe (EU and United States) for payments, with no access to your tax documents. The two I run myself, on that same Swiss infrastructure and as open-source software rather than a service bought in, are Supabase for the database, sign-in and file storage, and, since 19.08.2026, the Plausible analytics software. That one sets no cookies and collects no personal data, which is why taxwize.ch has no cookie banner.

Question 6: What can I demand if I want to know exactly?

You aren't limited to what a provider publishes voluntarily. Under Art. 25 of the Swiss Data Protection Act, whose revised version has been in force since 01.09.2023, you can request information at any time about whether and which personal data is being processed about you. The information is in principle free of charge and is normally provided within 30 days (source: FDPIC, right of access, retrieved 25.07.2026). Rights to rectification and to deletion come on top.

In practice an informal email to the provider's data-protection address is enough to start it. How fast and how completely they answer is itself an answer. At TaxWize the address is privacy@taxwize.ch.

The six questions at a glance

What happens to your salary certificate after you upload it

Say you upload your salary certificate for tax year 2025. From there:

1. The file travels encrypted over TLS to a server in Switzerland and is placed in Swiss document storage with access controls.
2. If the page is a scan or a photo, self-hosted text recognition turns the image into text, on the same Swiss infrastructure.
3. The Swiss-hosted language model reads the text and proposes the values, for example the gross salary or the AHV deduction.
4. Every proposed value can be viewed, corrected or discarded before the calculation.
5. The tax calculation applies your canton's stored rules to those verified values and produces the same figure every time for the same inputs.
6. If you later delete everything, the document and the extracted values disappear from the live systems immediately, the backups within 30 days.

Everything in this article is as of 24.08.2026. Prices, deadlines and service providers move, so the linked pages carry the current version.

Where other routes come out ahead

The official cantonal portal is the most data-frugal option available. Your tax office already holds your tax data, so no additional party enters the picture. If data minimisation matters to you above everything else and you're happy to sort and type every figure yourself, your canton's portal is the right route. I did our own returns for years before I started building any of this, first in the canton of Zurich and, after the 2023 move, in Aargau, on paper and with desktop software. Any preparation layer in front of the portal, TaxWize included, is a deliberate trade-off: more convenience against one more party you entrust with data.

Paper and local software still have their place. If you'd rather upload nothing at all, working locally remains open to you, and as long as your canton offers a local version it stays a legitimate choice, even though the trend runs towards web solutions.

Not everything on the TaxWize side is spotless either. Payment processing leaves Switzerland. There's also the optional "Sign in with Google" button, which processes no tax data but is still a service from an international provider. Payment processing is written out on the data-protection page and the Google button on the security page, both in plain sight rather than in fine print. TaxWize has carried the "swiss hosting" and "swiss made software plus AI" labels since August 2026. Both rest on my own declaration, with no outside audit behind them, so I call them labels and not certifications.

What this means for your choice

The six questions work on any provider, TaxWize included. Answers on a public page, concrete and with names rather than adjectives, are a good sign. Answers you only get by asking are still fine. If you don't get them at all, you know enough.

TaxWize costs CHF 39 for one declaration in one tax year and currently covers seven cantons with full preparation. Filing still happens with your canton afterwards. All six answers sit on the data-protection page and the security page before you create an account. If you'd first just like to know what your municipality means for your tax bill, that works with no upload and no account in the free tax comparison. And what else is out there, with prices and sources, is in the 2026 comparison of software and services.