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Compliant e-invoices in one POST request. Generate, validate and parse XRechnung and ZUGFeRD / Factur-X. Made in Germany, hosted in the EU.

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© 2026 VIBOA UG (haftungsbeschränkt) · HannoverDE · EN

Not legal or tax advice. XRechnung® is a standard of KoSIT; ZUGFeRD® of FeRD. Names used for format identification only.

DocumentationAuthenticationYour first invoiceThe 422 reportQuotas & limitsTest vs. live keys
API referencePOST…/generatePOST…/validatePOST…/parse
ReferenceError codesValidation rulesInteractive referenceOpenAPI spec↗

API errors

The invoice is not valid

Your request was well-formed, but the generated (or submitted) document failed e-invoice validation. The response carries a full report with one entry per finding.

Error type
https://normbill.com/docs/errors/validation-failed
HTTP status
422

Common causes

  • A mandatory XRechnung element is missing — for example the buyer reference / Leitweg-ID (BR-DE-15) or seller contact details (BR-DE-2).
  • Supplied totals do not match the computed amounts (BR-CO-10/13/15).
  • VAT category and rate are inconsistent (for example a standard-rated line with rate 0).

How to fix it

  • Work through report.issues: each issue has the rule id, the path in your request JSON, a plain-language message and a concrete fix.
  • Follow each issue's docs_url for a per-rule explanation (/docs/rules/<rule-id>).
  • Fields you omit are computed or defaulted where possible — consider removing invoice.totals and letting normbill compute them.

The error response format

Every non-2xx response from the API is an RFC 9457 problem-details body (application/problem+json) with at least type, title, status and detail. The type URL links back to this reference.

All error slugs: invalid-request, bad-request, payload-too-large, unauthorized, validation-failed, unparseable-document, plan-limit, quota-exceeded, rate-limited, overage-cap-reached, validate-fair-use, idempotency-key-invalid, idempotency-key-reuse, idempotency-conflict, pdf-unavailable, validator-unavailable, not-ready. Still stuck? Email support@normbill.com or start at the docs overview.