- From February 2026, the Polish National e-Invoicing System (KSeF) will be mandatory for most businesses, fundamentally changing how invoices are issued, validated, and exchanged. KSeF checks invoices for compliance with the official XML schema, ensuring all mandatory fields are present. It enforces unique invoice detection by checking the seller’s NIP, invoice type, and number. The invoice date cannot be later than the receipt date by KSeF. There are file size and batch restrictions, with encryption standards requiring AES-256-CBC and RSAES-OAEP. Metadata validation ensures file integrity, and attachments are allowed only in batch mode. Invoices must be submitted by authorized individuals, with permissions granted via the ZAW-FA form or delegated by someone with primary rights.
Source: vatcalc.com
Note that this post was (partially) written with the help of AI. It is always useful to review the original source material, and where needed to obtain (local) advice from a specialist.
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