A state system in which invoices are issued, stored and received in a defined XML format (FA(3)). Each invoice gets a KSeF number and the issuer receives an official receipt confirmation (UPO).

KSeF: who does it apply to?

Polish entrepreneurs who issue invoices to other businesses and receive purchase invoices. The mandate covered companies in stages, with a later date for the smallest ones.

KSeF: when and by what deadline?

You send an invoice to KSeF when you issue it. Current mandate dates and transition periods are described in the “KSeF regulations” category of the legal chronicle.

KSeF: where do you file or arrange it?

In invoicing software connected to KSeF or in the Ministry of Finance's free tools. Access is granted by a KSeF token or certificate.

KSeF

KSeF: what is it?

National e-Invoice System

KSeF is the Ministry of Finance's nationwide system for issuing and receiving structured invoices. The mandate has been introduced in stages.

What it is: A state system in which invoices are issued, stored and received in a defined XML format (FA(3)). Each invoice gets a KSeF number and the issuer receives an official receipt confirmation (UPO).
Who it affects: Polish entrepreneurs who issue invoices to other businesses and receive purchase invoices. The mandate covered companies in stages, with a later date for the smallest ones.
When: You send an invoice to KSeF when you issue it. Current mandate dates and transition periods are described in the “KSeF regulations” category of the legal chronicle.
Where: In invoicing software connected to KSeF or in the Ministry of Finance's free tools. Access is granted by a KSeF token or certificate.

How it works in Zaksio

Zaksio issues invoices with submission to KSeF, downloads the UPO and purchase invoices, and prints QR codes.

This is information, not legal advice. As of 2026-10. Deadlines and rules may change, so check them in the official source.

Source: Tax Portal: National e-Invoice System

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Key answers

How it works in Zaksio

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