Frihet is already KSeF compliant — Poland's mandatory e-invoicing system
KSeF (Krajowy System e-Faktur) is Poland's centralized e-invoicing system. From February 2026 it is mandatory for large companies and from April 2026 for all VAT payers. Frihet connects directly to the KSeF API.
What is KSeF and why is it mandatory?
KSeF is Poland's national structured e-invoice system, managed by the Polish Ministry of Finance. Unlike Peppol, KSeF is a centralized system: all invoices go through the government's central registry, which validates them, assigns a unique identifier (KSeF ID), and archives them. Only invoices with a KSeF ID have fiscal validity in Poland.
Feb 1, 2026
Date for large companies
Apr 1, 2026
Date for all VAT payers
KSeF API
Centralized system
KSeF implementation timeline
KSeF technical requirements
Format: FA(2) — national structured XML
Invoices must follow the FA(2) schema defined by the Polish Ministry of Finance. It is a proprietary XML format, based on EN16931 principles but with national structure.
Submission via KSeF API
All invoices are sent directly to the Polish government's centralized KSeF API. The API assigns the KSeF ID to each accepted invoice.
Mandatory KSeF ID
Each invoice receives a unique KSeF ID that must be included in any related commercial communication and in accounting records.
Authentication with digital signature
Access to the KSeF API requires authentication via digital certificate or authorization token generated by the Polish administration.
How Frihet handles KSeF compliance
Frihet integrates directly with the KSeF API so you don't have to worry about the technical complexity.
Automatic generation in FA(2) format
Frihet automatically generates invoices in the FA(2) XML schema required by KSeF when the recipient is a Polish VAT taxpayer.
Direct submission to the KSeF API
Frihet connects directly to the Polish government's KSeF system API, handling authentication and invoice submission with no additional intermediaries.
Receipt and management of KSeF ID
Once the invoice is accepted by KSeF, Frihet stores the assigned KSeF ID and links it to the invoice in your system. The KSeF ID is available for all related documents.
Receipt of KSeF invoices from suppliers
Frihet also handles receiving invoices from your Polish suppliers sent through KSeF, automatically importing them into your accounting.
FAQ — KSeF Poland
What is the KSeF ID and why is it important?
The KSeF ID is the unique identifier assigned by the KSeF system to each accepted invoice. Without a KSeF ID, an invoice has no fiscal validity in Poland after the mandate dates. It is also required for VAT refund claims and accounting records.
Does KSeF affect foreign companies selling in Poland?
The KSeF mandate affects all companies registered as VAT payers in Poland, regardless of their headquarters. If you have a Polish VAT number (NIP), you must use KSeF. If you sell in Poland without being registered there, the mandate does not directly apply to you.
What happens if I send an invoice without using KSeF after the mandate?
Invoices issued outside the KSeF system after the mandate dates have no legal validity in Poland. The recipient can reject them and the issuer may face sanctions from the Polish tax administration (KAS).
Do I need a Polish digital certificate to use KSeF?
To access the KSeF API, authentication is required, which can be via qualified Polish digital certificate or authorization token. Frihet manages this authentication process for you, simplifying technical access.
Does KSeF replace the obligation to retain invoices?
Invoices stored in KSeF are retained in the Polish government's system. However, companies still have the responsibility to maintain their complete accounting records. Frihet additionally archives all invoices with their KSeF metadata in your account.
Comply with KSeF starting today
Frihet connects directly to the KSeF API. Start free and manage your Polish invoices without technical complexity.
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