National e-Invoice System (KSeF) is primarily associated with cloud computing and real-time document circulation. But what happens when the system is unavailable, there is a failure, or when you receive an invoice "in hand" (e.g., as a consumer or foreign entity)?
That's when technology that connects the digital and analog worlds comes into play: 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 authenticate the seller when the system is "silent."
Although KSeF is a mandatory system mandatory (from February 1, 2026 for large companies, from April 1, 2026 for others), there are situations in which the invoice is not sent to you directly through the system, but is delivered in an "agreed manner" (e.g., PDF in an email or printout).
This happens when:
In such cases, the key to security is QR codes.QR codes (graphic codes that allow for quick data reading).
If you receive a paper or PDF invoice, it should contain a verification code (QR code). This solution allows for so-called two-step access.
How does it work?
This ensures that the paper printout matches what the seller sent to the Ministry of Finance.
The situation becomes more interesting when the seller issues an invoice in OFFLINE (e.g. during a system failure). Such an invoice has not yet been sent to KSeF, so the system cannot confirm its existence. So how can you check if the document is not fake?
In this case, the invoice must include two QR codes:
In order for the seller to generate the second, key QR code ("CERTIFICATE"), they must have a special KSeF Type 2 Certificate (dedicated to sealing invoices offline).
Here we return to the fundamentals of digital trust:
Even when KSeF is "offline," digital trust services technology (qualified seals (QSeal), qualified signatures (QES), certificates) ensures the security of transactions. The QR code on the invoice is not just a decoration—it is your control tool.
To ensure that your company is ready to issue invoices in all circumstances (including during a failure), make sure you implement a qualified signature.qualified signature or electronic seal today. They will allow you to generate the necessary KSeF certificates.
We also invite you to contact podpisano.pl – we will help you secure your company's digital identity.
For more information on KSeF procedures, visit the official website ksef.podatki.gov.pl and in our knowledge base.
This article was prepared based on the KSeF 2.0 Handbook (Ministry of Finance, September 2025) and information from the website ksef.podatki.gov.pl.
Do you want to learn more about a specific digital trust requirement or service? We would be happy to help!
