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

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API errors

Too many requests (burst rate limit)

You sent requests faster than the burst rate limit allows. This is a short-term throttle, separate from your monthly quota — the quota is unaffected.

Error type
https://normbill.com/docs/errors/rate-limited
HTTP status
429

Common causes

  • A spike of requests under one API key exceeded the per-key burst limit.
  • Many requests from one client IP exceeded the per-IP backstop (which also catches unauthenticated or rotating-token traffic).
  • A retry loop without backoff is hammering the endpoint.

How to fix it

  • Slow down and retry after a short pause — the burst allowance refills continuously.
  • Add exponential backoff to your client and avoid tight retry loops.
  • Spread bulk work out over time instead of firing every request at once.
  • Note this is not your monthly allowance: quota-exceeded is the separate per-period limit.

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.