Poland switched to mandatory structured e-invoicing this year. Since 1 February 2026 for the largest companies, since 1 April 2026 for all active VAT payers, and from 1 January 2027 for everyone else, including the smallest and VAT-exempt. The system is called KSeF (Krajowy System e-Faktur).
Source: [Dev.to](https://dev.to/stackedboost/integrating-with-polands-ksef-five-things-that-arent-in-the-docs-4mff)