What a viewer actually does
An XRechnung is raw XML. A viewer translates this structure into a readable invoice picture — no more, but at least that reliably.
For the occasional look that is exactly right. You see what is in it without deciphering the code. Problems only arise when “occasional” becomes daily business.
The free options
The KoSIT XRechnung viewer is the official reference and free. Alongside it there are free tools like the Quba viewer and various online viewers in the browser.
All render the XML solidly. The difference is not in the display but in everything that comes after: validate, approve, assign, archive. A pure viewer by definition does not do that.
Where a viewer stops
Three limits always appear in practice. First the volume: uploading every file individually does not scale. Second validation: a viewer shows the invoice but does not say whether it is norm-compliant and complete. Third retention: looking is not archiving — the original is afterwards still somewhere in the mailbox.
A viewer solves the display problem. It does not solve the process problem.
Data protection with online viewers
Browser viewers are convenient. But you upload real supplier data — amounts, bank details, names — to a third-party server. For a one-off peek that may be acceptable. As a permanent solution for sensitive invoice data it is tricky, especially with regard to the GDPR.
Whoever processes invoices regularly should know where this data ends up — and not leave it to the chance of a free tool.
When more than a viewer is worth it
The rule of thumb is simple: as soon as displaying is no longer enough, the viewer is the wrong tool.
- Few invoices, only viewing → a free viewer is enough.
- Regular intake, validation needed → software or a dedicated inbox.
- GoBD-compliant retention required → a viewer is not enough, the original must be archived audit-proof.
- Sensitive data, data protection important → not arbitrary online viewers.
- Hand-over to the tax advisor → structured export instead of manual back and forth.