Numer KSeF (KSeF number)

The Numer KSeF is the identifier the Polish platform assigns to an invoice once the system has accepted it.

Definition

The Numer KSeF is the unique identification number generated by the Krajowy System e-Faktur (KSeF), Poland's national electronic invoicing system. It is assigned to each structured invoice once it has been submitted and accepted by the platform (a centralised clearance validation model).

This number identifies the invoice unambiguously within the national system.

Role

The Numer KSeF plays several key roles:

• it is the proof that the invoice was received and registered by KSeF;
• it serves as a stable reference to retrieve, cite or reconcile the invoice across supplier, buyer and tax authority;
• it marks the point at which the invoice is deemed issued and made available to the buyer in the system.

Good to know

The Numer KSeF is distinct from the commercial invoice number chosen by the seller: it is an identifier assigned by the platform, not by the business. Until an invoice has received its Numer KSeF, it is not considered validated by the system.

This number is typically carried over into payment references and reconciliation records linked to the invoice.