The rollout is phased: from 1 February 2026 the obligation will apply to the largest companies, from 1 April 2026 to all other entrepreneurs, and from 1 January 2027 also to the smallest entities. During the transition, large companies will need to operate two processes in Poland: invoices issued via KSeF and traditional invoices from smaller suppliers. Procedures should be prepared in advance to avoid confusion and duplicate work.