KSeF (National e-Invoicing System – what is it?

KSeF (National e-Invoicing System ) is a nationwide ICT platform operated by the National Tax Administration, where invoices are issued, transmitted, and stored in a structured electronic format. An invoice issued in KSeF is uploaded to the system, and the buyer downloads it from there, so it is no longer sent by email or in paper form.

KSeF is not an invoicing program. Companies do not issue invoices within the system itself, but rather from their financial and accounting software or ERP systems, which connect to KSeF and transmit data to it.

How KSeF works?

An invoice in KSeF is a structured invoice, i.e., an XML file compliant with the scheme published by the Ministry of Finance. The data is placed in strictly defined fields, allowing it to be read automatically without manual transcription. The PDF version of the invoice is for reference purposes only and does not constitute an invoice as defined by law.

The issuer sends the invoice to KSeF, where the system verifies its compliance with the schema; if it is valid, the system assigns it a unique KSeF number. From that moment on, the invoice is considered issued and delivered to the buyer, and the buyer retrieves it from the system using their own access credentials. Invoices are stored in KSeF for many years, so a company can retrieve them without having to search through its archives. In the event of a system failure or unavailability, contingency procedures are in place that allow an invoice to be issued outside of KSeF and uploaded to the system later.

Who is affected by KSeF, and when does it take effect?

The requirement was introduced in stages:

  • as of February 1, 2026 – all businesses must receive invoices via KSeF, and the largest companies with annual sales exceeding 200 million PLN must issue invoices through it,
  • as of April 1, 2026 – the requirement to issue invoices applies to all other businesses,
  • as of January 1, 2027 – the requirement also applies to the smallest companies whose monthly sales do not exceed 10,000 PLN.

Detailed rules, including exceptions and transitional provisions, depend on the type of business and are subject to change; therefore, it is advisable to check them in announcements from the Ministry of Finance.

KSeF and invoice workflow in a company

For companies, KSeF primarily changes the way invoices reach the organization. Invoices are no longer received via email in various formats, but as structured data retrieved from a single source. If a company has a document workflow system integrated with KSeF, it can automatically retrieve such invoices, route them for review and approval according to established rules, and then forward them for posting in the financial and accounting system. With a large volume of invoices, this means less manual work and fewer errors, while also requiring that the processes for receipt, approval, and posting be well organized.