KSeF FA(3) e-invoice API for Poland

Polish KSeF FA structured invoices. Generate and validate the FA XML your own system submits to Krajowy System e-Faktur.

KSeF is Poland’s national e-invoice system. The structured file is FA XML (the FA(3) generation in current rollouts), not Peppol UBL.

The API generates and validates that FA XML from your invoice JSON. Your application still authenticates to the Ministry of Finance gateway and submits the file. EInvoiceFile does not hold a KSeF session for you.

Where it applies

• Poland · KSeF 2.0. Structured FA invoices for B2B through the Ministry of Finance gateway
• EU · EN 16931. Map from Peppol / UBL / CII into the national FA schema
• Cross-border · Optional. Use convert endpoints when the buyer is outside KSeF

Sample JSON

{
  "invoice": {
    "number": "FA/2026/0042",
    "issueDate": "2026-09-04",
    "currency": "PLN",
    "seller": { "name": "EInvoiceFile Sp. z o.o.", "nip": "5252345678" },
    "buyer": { "name": "Acme Polska", "nip": "1132456789" }
  }
}

Download sample XML · API reference

Related

• Poland e-invoicing
• JSON to KSeF
• API reference

Questions