The National e-Invoicing System (KSeF) is primarily associated with cloud-based operation and real-time document circulation. But what if the system is unavailable, there is an outage, or you receive an invoice „in hand” (e.g., as a consumer or foreign entity)?
That's when the technology that connects the digital and analog worlds enters the scene: QR codes and KSeF Certificates.
Today we explain how the two-step invoice access mechanism works and why Qualified Electronic Signature (QES) is necessary to give credibility to the vendor when the system is „silent.”.
Although the KSeF is a system obligatory (as of February 1, 2026 for large companies, as of April 1, 2026 for others), there are situations where the invoice does not come to you directly through the system, but is transmitted in an „agreed manner” (e.g., a PDF in the mail or a printout).
This happens when:
In such cases, the key to safety is kQR codes (Graphic codes that allow fast reading of data).
If you receive a paper or PDF invoice, it should contain a verification code (QR Code). This solution allows you to so-called. two-step access.
How does it work?
This way you can be sure that the paper printout coincides with what the vendor sent to the Ministry of Finance.
The situation becomes more interesting when the seller invoices in the mode of OFFLINE (e.g. during a system failure). Such an invoice has not yet gone to KSeF, so the system cannot confirm its existence. So how to check if the document is not fake?
In this case, the invoice must include as many as two QR codes:
In order for a retailer to generate this second key QR code („CERTIFICATE”), it must have a special Type 2 certification KSeF (dedicated to sealing offline invoices).
Here we return to foundations of digital trust:
Even when KSeF is „offline.”, digital trust services technology (qualified seals (QSeal), qualified signatures (QES), certificates) watches over the security of trading. The QR code on the invoice is not a decoration - it is your control tool.
To ensure that your company is ready to issue invoices under any conditions (including during an emergency), make sure you implement the following kvalified signature or electronic seal today. They will allow you to generate the necessary KSeF Certificates.
You are also welcome to contact podpisano.pl - We will help you secure your company's digital identity.
For more information about KSeF procedures, visit the official website ksef.podatki.gov.pl And in our knowledge base.
The article is based on Handbook KSeF 2.0 (MF, September 2025) and information from ksef.podatki.gov.pl.
Do you want to learn more about a specific digital trust requirement or service? We would be happy to help!
