PaperTax Beta: A Copilot for your Swiss Tax Return

J

j-p-zu

New member
Hi all,

We built PaperTax as a preparation and advisory layer that guides you through your official cantonal app (like VSTax or ZHprivateTax).

Why we built it (a real story from our last 3 years):
  • Year 1: we hired a paid fiduciary (Treuhänder). They claimed hardly any deductions, and entered about CHF 13k of income twice (a maternity leave certifcate already inside the salary certificate).
  • Year 2: then we decided to use AI and we found more deductions than the fiduciary.
  • Year 3 (2025): used our own app. It claimed the most deductions so far and caught the income the fiduciary had double-entered.

It assists you in different moments of tax preparation
  • it pre-screens documents against your cantonal thresholds to tell you what is not even worth entering.
  • it gives line-by-line guidance for each document.
  • it converts IBKR, DEGIRO, Charles Schwab, or Swissquote positions directly into the Swiss eTax statements (e-Steuerauszüge).
  • it catches discrepancies, in our own filing it flagged a vehicle we had forgotten, because we had no source document to remind us.

Our limits and the beta program:

PaperTax provides specific guidance, but it is not a guarantee. In our internal testing, the system has missed certain complex deductions. We are working to resolve these edge cases, which is why we are opening a beta phase for users to test and shape the development of the app.

Beta access is available for CHF 5 (normally CHF 50) with the code BETA90. To give it a try visit https://papertax.ch

Pablo.
 
Hi

Thanks for sharing. It looks like an interesting, cheaper alternative to a fiduciary for people that still need help.

Since this is highly sensitive data, how do you protect the data of the customers?
 
Hi Baptiste,

Thank you for asking. It is the most important question to ask regarding a tool like this.

We rely on strict data locality and minimal retention. Here is exactly how user's data is handled:
  • Swiss Data Locality: All uploaded documents and session data are stored exclusively in Switzerland, hosted in our Supabase Zurich instance.
  • Zero AI Training: We use Anthropic's Claude to process the documents and guide the inputs. Your documents and session context are completely isolated and are never used to train any AI models.
  • Strict 24-Hour Deletion: We do not want to hold your documents permanently. They are automatically deleted 24 hours after you finish your tax return. If you prefer, you can manually delete your data at any time, which purges it immediately.
  • Complete Erasure: If you choose to delete your account, all associated data is permanently removed from the database.

You can check further details at our Trust page.

I am happy to answer any other technical questions you or the community might have.

Pablo.
 
j-p-zu said:
We built PaperTax as a preparation and advisory layer that guides you through your official cantonal app (like VSTax or ZHprivateTax).
Click to expand...
Thanks for sharing.

Being fully aware of security vs. convenience but also self responsibility, here are a few of my thoughts:
  • You write "Swiss storage". I think this is not the fully story since Anthropic transfers the data to the US for processing.
  • Mistakes/haluzinations of AI: how do you handle this? Do you provide a recommendation about the reliability of your results? Something like: "we are highly confidant that we have understood your numbers correctly and our advice represents current laws and regulations." vs. "We have doubts that we were able to understand and process your numbers or have a complex situation. We therefore suggest to take a further step to verify or consult with a tax advisor."
  • You write: "Encrypted at rest". Does that mean that you have access to the keys and could potentially get clear text access to the data?
  • Personally, I would prefer to see the name (and potentially a photo) of the people who are behind it.
 
Hi Gaijin, Amir here from PaperTax, you raise good points. Let me address them directly.

Regarding "Swiss storage" vs. US processing, you are right.
Our data is stored in Switzerland using Supabase in Zurich.
However, to read and understand your documents, they are sent to Anthropic's Claude AI, which is located in the US.
This means while processing, your data leaves Switzerland. It's important to note that Anthropic does not use this data to train their AI.
So while "stored in Switzerland" is true, it doesn't tell the full story. It's where the data sits when not being processed, but not where processing takes place.
The important thing for us is that we use trusted subprocessors like Supabase and Anthropic and make sure the user's documents can always be completely erased after processing.

When it comes to AI mistakes and reliability, we acknowledge this is a risk and we're upfront about it. PaperTax is an aid, not a guarantee.
Currently, we perform a second check on the final output to catch inconsistencies, and we make it clear that it can miss things in complex cases.
I appreciate your suggestion to explicitly mark what we're confident in vs. what users should double-check or ask an expert about.
This is the direction we want to move in. The key message for users should be: if it's complex or high-stakes, verify it or consult a professional.

On the topic of encryption and data access, I want to be completely honest: yes, technically we can access the data.
"Encrypted at rest" protects the stored data, but it's not end-to-end encryption.
We manage the keys, and for the app and AI to read your documents, the data has to be unencrypted during processing.
We keep each user's data separate and have no interest in people's files. However, we won't claim we can't see it when we can.
This is the real trade-off of an AI tool that needs to understand your documents.

Regarding our identities, you're right, we should be visible. We are Amir and Pablo (https://www.linkedin.com/in/amirmohammadi/, https://juanpzuluaga.github.io/). We'll add our names and photos to the website so people know who is behind this.
As for why we built it: we struggled with our own Swiss taxes and wanted to make the process better.

We appreciate your careful scrutiny. This is exactly why we opened this beta.
 
Thanks, @papertax !
Nothing surprising, everything as I expected :)
It's tricky. People who already use AI a lot could perform this check themselves. I'm sure many people already upload their tax statements to AI to get a second opinion. People who don't use AI yet will be harder to convince to trust AI with their sensitive data.
 
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