Validation rules

BR-O-01 — EN 16931 rule

Lines or document-level allowances/charges use VAT category "O" (not subject to VAT), so the VAT breakdown (BG-23) must contain exactly one such entry.

Rule: BR-O-01 — official EN 16931 / XRechnung rule
Severity: error
Business term: BT-151 — Line VAT category
Field in your JSON: invoice.lines[*].vat_category
Detected by: tier 3 — KoSIT validator (authoritative)
Reachability: Triggerable from your request JSON (generate & validate)

normbill derives one breakdown per category and rate, so generated documents only violate this when O items carry differing vat values.

How to fix it

Omit line.vat on every O line (and vat on O allowances/charges) — normbill then emits exactly one O breakdown.

BR-O-01 auf Deutsch — was bedeutet der Fehler?

Positionen oder Nachlässe/Zuschläge verwenden die Kategorie "O" (nicht umsatzsteuerbar), also muss die Umsatzsteueraufschlüsselung (BG-23) genau einen O-Eintrag enthalten. Bei normbill passiert das nur, wenn O-Positionen unterschiedliche vat-Werte tragen.

So beheben Sie den Fehler

Lassen Sie line.vat auf allen O-Positionen (und vat auf O-Nachlässen/-Zuschlägen) weg — normbill erzeugt dann genau eine O-Aufschlüsselung.

Related rules

BR-O-11 — VAT category "O" (not subject to VAT) cannot be mixed with other VAT categories on the same invoice…
BR-CO-04 — An invoice line is not categorized with a VAT category code (BT-151).
BR-AE-01 — Lines or document-level allowances/charges use VAT category "AE" (reverse charge), so the VAT breakdown…
BR-B-01 — VAT category "B" (Italian split payment) is only allowed on domestic Italian invoices — every country code…
BR-B-02 — VAT category "B" (Italian split payment) must not be combined with category "S" (standard rated) on the same…
BR-E-01 — Lines or document-level allowances/charges use VAT category "E" (exempt), so the VAT breakdown (BG-23) must…

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.

Or try it live: drop any XRechnung XML on the free validator — same KoSIT-backed report, no account.