Mandate · Poland

KSeF: Poland's national e-invoicing system, and why it is not EN 16931

KSeF is not a Polish implementation of EN 16931, and it is not UBL with different tag names. It is a separate national schema, and most of what trips people up about its 2026 rollout is assuming otherwise.

From 1 February 2026, every taxpayer must be able to receive invoices through KSeF. There is no size phasing on the reception side — the obligation applies to all taxpayers on that date, under the ustawa z dnia 5 sierpnia 2025 r. amending the VAT act (Dz.U. 2025 poz. 1203), and KSeF 2.0 went into production that day.

Issuing is phased, and the reference year is 2024

The obligation to issue through KSeF is phased by turnover. It is not phased by company size category. Article 145l of the act lets a taxpayer keep issuing electronic or paper invoices outside KSeF between 1 February and 31 March 2026 only if its total sales including VAT did not exceed PLN 200,000,000 in 2024. In practice, the issuing obligation starts on 1 February 2026 for taxpayers whose 2024 sales including VAT exceeded that threshold, and on 1 April 2026 for everyone else.

Two reliefs run through the end of 2026

Article 145m lets a taxpayer keep issuing electronic or paper invoices from 1 April to 31 December 2026 where the monthly value invoiced that way is PLN 10,000 gross or less. The right is lost from the invoice that breaches the cap. It is not lost from the start of the following month. Separately, article 145n lets invoices issued via cash registers, and fiscal receipts bearing a NIP treated as simplified invoices, continue until 31 December 2026.

No penalties in 2026

The KSeF penalty regime, article 106ni of the act, does not enter into force until 1 January 2027. Every date above describes when an obligation begins. It does not describe when a sanction for missing it starts.

This calendar has already moved twice

The dates above are not the first version. An earlier act, ustawa z 16 czerwca 2023 r., set mandatory KSeF at 1 July 2024. That date was suspended in January 2024 and formally removed by ustawa z 9 maja 2024 r. (Dz.U. 2024 poz. 852). The 1 February / 1 April 2026 dates come from the later, August 2025 act described above, and are the ones currently in force.

The schema is FA(3), and it has nothing to do with EN 16931

KSeF invoices are structured to FA(3), published 25 June 2025 in the Centralne Repozytorium Wzorów Dokumentów Elektronicznych, wzór http://crd.gov.pl/wzor/2025/06/25/13775/. FA(3) replaced the prior FA(2) schema from 1 February 2026. Its root element is Faktura, and its namespaces are Ministry of Finance domain types plus W3C XMLSchema; no UBL, no UN/CEFACT CII, and no EN 16931 anywhere in it. An EN 16931 invoice is not a KSeF invoice, and converting its syntax does not make it one; the two describe invoices using entirely different data models.

EN 16931 does exist in Poland, on a different rail

Poland's business-to-government channel for EN 16931 invoices is PEF (Platforma Elektronicznego Fakturowania), a Peppol-based system implementing Directive 2014/55/EU. PEF and KSeF are two separate systems serving two separate obligations; an invoice built for one is not automatically valid on the other.

One further instrument sits behind the reception date: Council Implementing Decision (EU) 2022/1003 of 17 June 2022 authorised Poland to derogate from articles 218 and 232 of Directive 2006/112/EC, for the period 1 April 2023 to 31 March 2026.

What this does not cover

EUInvoice does not transmit invoices to KSeF and does not produce FA(3) documents. This article does not cover the KSeF API, authentication to KSeF, or KSeF's offline modes; each is a separate, detailed topic on its own.