Poland e-invoicing — KSeF & the FA(2) → FA(3) structure
Poland's Krajowy System e-Faktur (KSeF) becomes mandatory in 2026: from 1 February 2026 for large taxpayers (PLN 200m+ turnover in 2024) and from 1 April 2026 for everyone else; digitally-excluded micro-businesses follow on 1 January 2027. Invoices use the FA logical structure — FA(3), in force since 1 February 2026, is the structure for the 2026 KSeF rollout (it replaced FA(2)).
FA(3) is the structure in force for the 2026 KSeF rollout. FA(3) validation is on the eleata roadmap — this page is guidance for now. The FA structure is XSD-based; we will validate against the Ministry of Finance schema plus the KSeF 2.0 logical-structure rules.
The timeline
1 February 2026 — mandatory for taxpayers whose 2024 sales (incl. VAT) exceeded PLN 200 million.
1 April 2026 — mandatory for all remaining taxpayers.
1 January 2027 — taxpayers issuing only small invoices / 'digitally excluded' micro-businesses come into scope; some simplifications (e.g. cash-register invoices, attachments) phase in around then.
Until the mandate date, KSeF is available on a voluntary basis; the Ministry of Finance runs a test environment.
The format: FA(2) → FA(3)
Invoices submitted to KSeF use the FA logical structure published by the Ministry of Finance (Ministerstwo Finansów) as an XSD. FA(3), in force since 1 February 2026, is the structure aligned with the 2026 mandatory rollout and the KSeF 2.0 API; it replaced FA(2).
KSeF assigns each accepted invoice a unique KSeF number; the structure and the API are versioned together (KSeF 2.0).
What to do now
Map your invoice data to the FA(3) XSD, test against the Ministry of Finance test environment, and integrate the KSeF 2.0 API for submission + status polling.
If you also trade cross-border via Peppol, keep your EN 16931 / Peppol BIS pipeline — KSeF is the domestic channel; it doesn't replace Peppol for cross-border.
Last updated 2026-05-12. This is general guidance, not legal advice — always check the official source for your situation.