National e-Invoice System (KSeF)
new integration libraries for
JAVA and .NET

We are very pleased to announce that we have released two more client libraries for the languages JAVA and .NET, which facilitate and accelerate the integration of systems with the National e-Invoice System. These are the next tools after the interface KSeF REST API and PHP librarythat we make available to our customers.

Of course, for the purposes of smooth integration, we have also prepared a detailed Technical Documentation together with a description of the business processes within which the use of individual operations is described. We encourage you to read the prepared description and diagrams.

We would also like to inform you that we are also starting intensive work on adapting our API interface to the changes that are to come into force in the near future. More about all these changes related to the adoption by the Council of Ministers on June 17, 2025. Draft Act on KSeF, you can read in our other article, in which we have included an analysis of all the most important issues: "Mandatory KSeF in 2026: Comprehensive guide to legal, organizational and technical implementation” .

We hope you enjoy reading.

The ksefapi.pl team