VaSt — Retrieving tax data with explicit storage rights

Bitbrew built an integration for Germany’s pre-filled tax declaration service, VaSt. The channel provides access to information already held by the tax authorities, including wage data, personal information and relevant certificates for a tax case.

Retrieving that information is only one part of the problem. VaSt also distinguishes between permission to access data and permission to retain it inside another system. A robust integration must model those rights independently rather than assuming that every successful retrieval automatically authorises permanent storage.

Data provenance matters as well. Where authoritative tax-office information is available, it takes precedence in the relevant context and should not be silently overwritten by older or conflicting local values. The application therefore needs to preserve which information originated from the authority and how it feeds into the existing case.

VaSt is not the electronic tax-office inbox and it is not the ELSTER filing channel. It is a distinct retrieval service with its own permission model. That separation makes the component reusable across tax applications: an existing system can consume pre-filled authority data while keeping retrieval, retention rights and professional processing as explicit concerns.