What are the current KSeF rate limits?

The Ministry of Finance publishes the authoritative list at https://ksef-test.mf.gov.pl/document/LimitValues/1.3/PL. Limits are per-endpoint and per-NIP context, and change between KSeF versions. Do not hardcode values — pull and cache the published document.

Does 21121 count against my invoice delivery SLA?

In practical terms, yes — a rejected request is not a submitted invoice. If your ERP does not retry with proper backoff, the invoice can sit undelivered for hours. Under mandatory KSeF this affects VAT booking timelines.

Can Invoice Navigator absorb 21121 for me?

Yes. Invoice Navigator paces submissions under the published quotas per NIP and per endpoint, retries with jitter, and only surfaces a 21121 to your ERP if the burst is genuinely unsustainable (typically >10× your provisioned throughput).

Do batch endpoints share the same quota as /online/Invoice/Send?

No. Batch endpoints have their own quota and much higher effective throughput per unit of quota. For any workload over ~500 invoices per hour, use /batch/Invoice/Send with Pakiet packaging.

Should I add multiple technical users to raise my limit?

Limits are per NIP context, not per technical user. Adding tokens does not raise your quota. To raise effective throughput, use batch endpoints or split across NIPs where legally permissible (e.g., separate legal entities).

Error codes · ksef · Poland

KSEF-21121Partly

KSeF rate limit reached for this endpoint

This is the rejection, word for word: „[KSEF-21121] KSeF error 21121 ("Limit żądań osiągnięty") is returned when the calling context exceeds the per-endpoint request quota published by the Polish Ministry of Finance. The API rejects the request with HTTP 429 and the client must back off before retrying. Quotas are applied per NIP context, per endpoint, and per time window.“

The Ministry publishes current limits at https://ksef-test.mf.gov.pl/document/LimitValues/1.3/PL. Limits differ between environments (test vs production) and between endpoints — /online/Session/AuthorisationChallenge, /online/Invoice/Send, /online/Query/Invoice/Sync, and batch endpoints each have their own bucket. The response includes a Retry-After header when a wait time is defined.

What to have readyThe correct figures from your bookkeeping; we show you which field is affected.

What we doImplement client-side rate limiting with the published per-endpoint quotas, honour the Retry-After header, and stagger bulk workloads across multiple contexts or across time. Do not retry immediately.

Choose the rejected invoiceor drop it here

XRechnung XML or ZUGFeRD PDF. Checking is free · corrected file €1.90 · the first every 30 days is free · no sign-up.

What the finding looks likeExample

FindingNeeds your check · KSEF-21121

From youThe correct figures

ThenChecked again

ProofSHA-256 and /verify link after the check

Often appears together with

KSEF-21116KSeF authentication token is invalid KSEF-21170KSeF interactive session has expired KSEF-21301Missing authorization for this KSeF operation