Poland made its National e-Invoice System, KSeF (Krajowy System e-Faktur), mandatory in 2026: from 1 February for the largest taxpayers and from 1 April for most other businesses, with simplified arrangements for the smallest. Unlike Belgium's network model or France's platform model, KSeF is a central clearance system. Invoices are uploaded to a government platform, validated, given a KSeF number, and only then delivered to the buyer.
How a KSeF invoice works
- The seller generates the invoice in the official XML schema (known as FA(3)).
- The invoice is sent to KSeF, usually directly from accounting or ERP software through the API.
- KSeF validates the file and assigns a unique KSeF identifier. The invoice is legally issued at that moment.
- The buyer downloads the invoice from KSeF, again usually through their software.
The invoice that matters is the XML stored in KSeF. There is no "original" sitting in someone's mailbox.
Where PDFs fit
Customers and colleagues still like to see an invoice. Polish practice uses visualisations: PDF renderings of the KSeF invoice, often with a QR code that links to the record in KSeF so anyone can verify it. If you receive one of these, treat it as a view. The QR code and KSeF number are what make it checkable.
PDFs are still common for:
- Invoices to consumers, which are outside the mandatory scope.
- Supporting documents attached to an invoice's context, such as contracts and delivery confirmations.
- Internal approval packs before payment.
What foreign companies should check
- Do you have a fixed establishment in Poland? Foreign businesses without one are generally outside the obligation to issue through KSeF, but rules for permanent establishments are nuanced, so confirm with a Polish tax adviser.
- Are your Polish customers asking for KSeF numbers? Buyers increasingly need them to match payments and deductions.
- Can your finance team read visualisations? Make sure AP staff know that the QR code verifies the invoice, not the logo or layout.
Watch out for fake visualisations
A PDF that looks like a KSeF invoice is easy to forge. Fraudsters already send convincing invoice PDFs with altered bank details. Before paying a new or changed account, scan the QR code, confirm the record in KSeF, and verify bank details through a known contact. Our guide to invoice fraud and business email compromise covers the warning signs.
Archiving
Invoices stored in KSeF are retained by the system for ten years, which changes how much Polish businesses need to archive themselves. Your own approval records, signed contracts and correspondence are still yours to keep. Store them as PDF/A for longevity; see PDF/A explained.
Takeaway
KSeF moves the invoice out of the inbox and into a central register. For anyone dealing with Polish businesses, the habit to build is simple: trust the KSeF number and the record behind it, and treat every PDF as a convenient picture of that record. For other European mandates, see Belgium and France.
