KSeF API Gateway

Integration gateway for Poland's National e-Invoicing System — simplified REST API, monitoring, queuing, and automatic retry.

What is KSeF API Gateway?

KSeF API Gateway (ksefapi.com) is a middleware layer between your system and the National e-Invoicing System (KSeF) operated by the Polish Ministry of Finance.

Instead of integrating directly with KSeF — which requires handling session tokens, complex XML structures, XAdES signatures, and unstable government responses — you use a single, consistent REST API.

What you get

Simplified API — REST JSON instead of SOAP/XML
Automatic retry — resilient resubmission on KSeF errors or downtime
Queuing — bulk invoice submission with throughput control
Monitoring — real-time invoice statuses and webhook notifications
Validation — invoice verification before sending to KSeF
Multi-tenancy — one API account, multiple companies (NIPs)

Architecture at a glance

Your System  →  KSeF API Gateway  →  KSeF (Ministry of Finance)
  (REST/JSON)    (validation,          (XML, sessions,
                  queuing, retry)       signatures)

The gateway handles all the complexity of KSeF communication: opening/closing sessions, XML generation from JSON, status polling, UPO retrieval, and certificate management.

Environments

Environment	API URL	Auth URL
Demo	`https://demo.ksefapi.com`	`https://demo-auth.ksefapi.com`
Production	`https://gateway.ksefapi.com`	`https://auth.ksefapi.com`

Next steps

Start with Getting Started for a 5-minute quickstart, or jump to Authentication for full integration details.