A revolution in Polish accounting is just around the corner. From February 1, 2026 , the obligation use of the National e-Invoice System (KSeF) will apply to the largest companies, and from April 1, 2026 all other taxpayers.
Many people wonder, "How does it actually work behind the scenes?" Today, we're going to get into the technical details. We'll explain why your system ERP (enterprise resource planning system) needs a "digital ID," i.e., a qualified signature QES, in order to even begin communicating with the Ministry of Finance's system.
Before your accounting system sends the first invoice, you must "introduce yourself" to KSeF. This is the most important technical requirement to start with. The system must be sure that it is your company, and not someone impersonating it, that wants to grant permissions or send documents.
Specific methods are used for authentication in KSeF:
Why a qualified signature? Although a trusted signature is sufficient for manual login, what counts in business is automation. A qualified signature or seal is necessary to generate a so-called tokens or KSeF certificates, which are the "fuel" for your ERP system. Without them, your accounting program will not connect to KSeF automatically.
AUTHENTICATION METHOD In KSeF | INDIVIDUAL | NON-NATURAL PERSON (PNF) |
Trusted Signature / National node (from April 1, 2026) | YES | NO |
Qualified signature | YES | NO |
Qualified stamp | NO | YES |
Token (until December 31, 2026) | YES | YES |
KSeF certificate | YES | YES |
Integration is nothing more than connecting your sales system to the Ministry of Finance system using API (application programming interface). This allows invoices to be sent "automatically" in the background, without the need to manually log in to the government website.
For this magic to work, you need to perform a one-time configuration:
Sending an e-invoice is a process that takes a fraction of a second in an integrated system, but it is worth knowing what happens "under the hood":
The obligation enters in stages:
Until these dates, KSeF can be used voluntarily. The key is to prepare the system, people and authorizations so that the launch does not surprise the company.
Important! Invoices for consumers (B2C) remain outside the obligation to issue in KSeF (you can voluntarily), but if you conduct B2B sales - the obligation will cover you according to the thresholds/dates. Foreign entities without a permanent place of business in Poland are excluded from mandatory issuance. (Interpretations)
Technology can be unreliable, which is why KSeF provides for an OFFLINEmode. If you do not have access to the network, you can issue an invoice in your system, attach a special QR code to it (for this you need a KSeF Type 2 Certificate!), and send it to KSeF later—usually on the next business day.
Definitely yes! Although the Ministry provides a free "KSeF Taxpayer Application," it is mainly intended for the smallest companies that issue a few invoices per month. For medium and large businesses, manually rewriting invoices is a waste of time and a risk of errors.
Qualified Electronic Signature (QES) and Electronic Seal (QSeal) are the foundations that enable your ERP system to operate automatically, securely, and in compliance with the law.
Do you want to prepare your company for KSeF? We invite you to cooperate with us. We will answer your questions about cider services.
At podpisano.pl the necessary digital trust tools that will open the door to digital accounting for you.
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.
