Polish NIP in KSeF: the right number needs the right field
NIP versus NrID in Poland's FA(3): checking buyer identification before sending an invoice to KSeF.
A correct Polish NIP value is only part of the check. The buyer's number belongs in NIP within Podmiot2/DaneIdentyfikacyjne. Putting it in NrID is not an equivalent entry.
Number and field
The Ministry handbook states that the NIP field is the basis for making an invoice sent to KSeF available to the buyer. A Polish NIP should not be entered in other fields, such as NrID. This concerns a buyer using a Polish NIP tax identifier. Source: handbook §2.1.4.
What to check in your software
Before sending, compare the buyer's number with their details and inspect the generated XML field: Podmiot2/DaneIdentyfikacyjne/NIP. An “identifier” label alone does not show where the software stores the number. This is a practical check, not an additional handbook obligation.
If an invoice is missing from the buyer's view, establish the number and field in the XML. Report these details to the software provider or accounting office. Do not assume this is the only possible cause of missing access. This article does not prescribe how to repair an invoice already accepted by KSeF.
FAQ
Can a Polish NIP go in NrID?
Not in this scenario. The buyer's Polish NIP belongs in NIP within Podmiot2/DaneIdentyfikacyjne.
Which field makes the invoice available to the buyer?
The handbook identifies NIP in the buyer's identification details, rather than any field containing the same number.
Is this the same as using another company's NIP?
No. Here the correct number is in the wrong field. Another buyer's number is a separate problem.
Source and limits
KSeF 2.0 handbook, part II, August edition, checked 7 October 2026; cover legal position: 1 February 2026. This Polish-system article excludes foreign identifiers, correction procedures and any guarantee of restored access.