The revolution in Polish accounting is just around the corner. From February 1, 2026. obligation The use of the National e-Invoice System (KSeF) will cover the largest companies, and from April 1, 2026. All other taxpayers.
Many are wondering „how does it actually work from behind the scenes?”. Today we're getting into the technical details. We will explain why your system ERP (enterprise resource management system) needs „digital ID card”, i.e. qualified signature QES, to even begin a conversation 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 get started. The system needs to be sure that it is your company, and not someone impersonating it, that you want to grant authorizations or send documents.
Specific methods are used for authentication in KSeF:
Why a qualified signature? Although the Trusted Signature is sufficient for manual logins, in business it is the following that counts automation. A qualified signature or stamp is necessary to generate a so-called "seal". 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 | PHYSICAL PERSON | ENTITY THAT IS NOT A NATURAL PERSON (PNF) |
Trusted Signature /. National hub (as of April 1, 2026). | YES | NO |
Qualified signature | YES | NO |
Qualified Electronic Seal | NO | YES |
Token (until December 31, 2026). | YES | YES |
Certificate KSeF | YES | YES |
Integration is nothing more than connecting your sales system to the Ministry of Finance system by means of a API (application programming interface). This allows invoices to send themselves „by themselves” in the background, without having to manually log into the government website.
For this magic to work, you need to perform a one-time setup:
Sending an e-invoice is a process that happens in a fraction of a second in an integrated system, but it's worth knowing what's going on „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, so the KSeF provides for a mode of OFFLINE. If you don't have access to the network, you can issue an invoice in your system, stamp it with a special QR code (you need a KSeF Type 2 Certificate for this!) and send it to KSeF later - usually the next business day.
Definitely yes! Although the Ministry provides a free „Taxpayer Application KSeF”, it is mainly designed for the smallest companies issuing a few invoices per month. For medium and large business, manual transcription of invoices is a waste of time and a risk of errors.
Qualified Signature (QES) i Electronic Stamp (QSeal) are the foundations that allow your ERP system to operate automatically, securely and legally.
Do you want to prepare your company for KSeF? We invite you to cooperate with us. We will answer your concerns related to cider services.
On podpisano.pl you will find the necessary digital trust tools that will open the door to digital accounting.
The article is based on Handbook KSeF 2.0 (MF, September 2025) and information from ksef.podatki.gov.pl.
