What is KSeF?
Overview
KSeF (Krajowy System e-Faktur) is Poland's National e-Invoice System — a centralized platform run by the Ministry of Finance for issuing, receiving, and archiving structured electronic invoices.
Key Features
KSeF allows businesses to:
- Issue invoices in the standardized FA(3) XML format
- Authenticate the taxpayer before a session is opened; the session token itself is issued by the gateway after sign-in
- Track invoice transmission status in real time
- Maintain a legally compliant invoice archive
Biurko connects to KSeF in two ways — Profil Zaufany, or the files of a qualified electronic signature — both described in the article on connecting to KSeF.
Why It Matters
From April 1, 2026 the obligation to issue invoices in KSeF covers the remaining taxpayers — the largest businesses joined earlier, and the smallest firms only join in the final wave. Each structured invoice passes through KSeF, which makes the flow of invoices transparent and standardised.
The invoice, though, is only where a company's month begins. What follows it — the registers, the tax, the files for the tax office and the ZUS contributions — happens outside KSeF.