KSeF Integrator — one API for Poland's national e-invoicing.

Poland's mandatory National e-Invoicing System (KSeF) means every B2B invoice must pass through a government platform — with its limits, statuses, sessions and evolving specification. KSeF Integrator hides that complexity behind one stable API: your ERP, accounting or e-commerce system hands over a document, and the Integrator manages authentication, the interactive session, KSeF numbers and UPO retrieval.

Systems that cannot (or should not) produce a complete FA(3) XML file on their own can use a simplified API and flexible legacy-integration mechanisms — various file formats and ETL processes. Initial connection setup is handled by a desktop application that obtains the authorization token (a certificate in the future) and securely stores it in the solution.

Every document is validated against the current FA(3) schema before it leaves your infrastructure. But we don't stop there: built-in business validators check the consistency of the data — e.g. whether net and VAT amounts add up to the gross value, whether line-item totals match the invoice summary, and whether fields required for a given document type are filled in correctly.

Errors are caught on your side, with a readable description — instead of a rejection from the KSeF gateway and corrections made under deadline pressure. The Integrator also prevents duplicate invoices from being submitted to KSeF.

Once KSeF accepts an invoice and assigns its number, the Integrator notifies the source system itself — no periodic status polling required. A flexible filter mechanism decides which system receives the information.

Multiple channels are available: webhooks, e-mail, a message on an integration queue or bus, and files placed on a network resource (NFS, S3, WebDAV, FTP). Queueing and automatic retries make sure documents reach KSeF even after platform downtime.

The Integrator periodically checks KSeF for new purchase invoices for the configured tax IDs. Based on defined filters it routes each document — as XML together with a PDF visualization — to the right system, using the same channels as on the sales side: webhook, e-mail, integration queue or file storage.

The PDF visualization is compliant with the regulations and closely mirrors the official Taxpayer Application, so documents can go straight to accounting and contractors.

You can deploy the Integrator in any container environment on-prem (Kubernetes, OpenShift, Docker Swarm) or in the cloud (Azure, GCP, AWS); a SaaS model is also available. The development and maintenance process follows ISO 27001, 27017 and 27018 as well as OWASP recommendations (ASVS in particular).

We support the rollout end to end — from KSeF training, through mapping invoicing processes and mapping data to FA(2)/FA(3) fields (together with tax advisory), to process-change recommendations and end-to-end tests. We also support the self-invoicing authorization process.