KSeF Authentication

POST /auth/{environment}

Logs in (establishes a connection) to KSeF using a certificate associated with the user account. Initiates an interactive session and returns access tokens.

Path Parameters

Parameter	Type	Required	Description
environment	string	✅	test, demo, or prod

Response 200

{
  "accessToken": {
    "token": "eyJ...",
    "validUntil": "2026-04-18 23:00:00"
  },
  "refreshToken": {
    "token": "eyJ...",
    "validUntil": "2026-04-18 23:00:00"
  },
  "environment": "test",
  "nip": "9570429696",
  "subjectName": "C=PL, O=Company XYZ, CN=user@example.com",
  "shortName": "user@example.com",
  "authenticatedAt": "2026-04-11 23:00:00"
}

Field	Type	Description
accessToken	object	KSeF access token with an expiration date
refreshToken	object	KSeF refresh token (may be null)
environment	string	The KSeF environment used
nip	string	Company Tax ID (NIP)
subjectName	string	Full subject name from the certificate
shortName	string	Shortened subject name
authenticatedAt	string	Authentication date

Error Codes

Code	Description
401	Missing or incorrect credentials (Basic Auth)
403	Missing required role (admin or technical)
404	No active certificate for the given environment
500	Server or KSeF error