KSeF (Polish National e-Invoice System)

Poland’s central system for structured e-invoices: invoices are sent as FA(3) XML and receive a KSeF number.

Invoices are issued as XML in the FA(3) schema published by the Ministry of Finance and sent to KSeF through its API, which returns a KSeF number and an official confirmation (UPO). According to the Ministry, it is mandatory from 1 February 2026 for companies with 2024 sales above PLN 200 million and from 1 April 2026 for everyone else. Systems that issue invoices themselves, such as an OMS, a CRM or a SaaS, need their own integration.

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