Validation rules

BR-DE-28

The seller contact email (BT-43) does not look like an email address — exactly one @, at least two characters on each side, no leading/trailing dot.

Rule: BR-DE-28 — official EN 16931 / XRechnung rule
Severity: warning
Business term: BT-43 — Seller contact email
Field in your JSON: invoice.seller.contact.email
Detected by: tier 3 — KoSIT validator (authoritative)
Reachability: Only reachable when validating your own XML — normbill-generated documents cannot trigger it

The request schema already validates emails strictly (z.email), so generated documents cannot carry an implausible BT-43.

How to fix it

Correct invoice.seller.contact.email.

BR-DE-28 auf Deutsch — was bedeutet der Fehler?

Die E-Mail-Adresse der Ansprechperson (BT-43) sieht nicht wie eine E-Mail-Adresse aus — genau ein @, mindestens zwei Zeichen auf jeder Seite, kein Punkt am Anfang oder Ende. Der Validator meldet eine Warnung.

So beheben Sie den Fehler

Korrigieren Sie invoice.seller.contact.email.

Official sources

Every 422 from the API lists the rule id, the path in your request JSON, a plain-language message and a suggested fix — see the docs overview for the report format.