Adrien Kunysz, Sun, 23 Oct 2022 17:34 CEST
In several Swiss cantons, the municipality provides information about their residents to third parties upon request without requiring a justification. In particular this is true for personnal tax information in canton Zürich. You can opt-out but it is not automatic.
The relevant law for canton Zürich appears to be Gesetz über die Information und den Datenschutz (IDG).
Specifically for tax records, the Federal Tax Administration provides an overview of the situation in each canton. The Datenschutzbeauftragte des Kantons Zürich has a publication on the topic.
Residents of the city of Zürich can opt-out by contacting the municipality through their website.
This is how I phrased my request:
Subject: Daten und Adressperre
Pursuant to IDG Art. 22 I hereby request you do not share information about me to third parties. This includes but is not limited to my tax record as described in "Steuerausweis und Datensperre" and address. Please confirm reception and compliance at your earliest convenience.
For identification purpose, my AHV number is [REDACTED]
http://www2.zhlex.zh.ch/appl/zhlexr.nsf/0/F835D453C58B0263C12574B90025F03C/$file/170.412.2.0762.pdf https://docs.datenschutz.ch/u/d/publikationen/webartikel/steuerausweisund_datensperre.pdf
Regards, [NAME]
I later received a letter from the Population Office confirming my data block had been enacted. On their side, the Tax Office required me to fill out and sign a specific form. After I did that, I received another letter from the Tax Office confirming my request had been enacted.
I hope some people find this information useful.