errorPLubl-2.1

PL-R-004:KSeF session token invalid

KSeF API requires valid authentication token.

Fix this in your source system

MANUAL

KSeF API authentication token is invalid or expired. This is not an invoice content issue. Renew your KSeF session token through the KSeF API authentication process. Check your invoicing software KSeF credentials configuration.

See the step-by-step instructions below to fix this error manually.

Why This Error Matters

Authentication required for KSeF operations.

How to Fix It

1

Authenticate

Use qualified certificate or trusted profile

2

Get token

Call InitSessionBySignature

3

Use token

Include in subsequent API calls

Technical Details

KSeF API authentication

Common Causes

  • Expired token
  • Invalid certificate
  • Wrong authentication method

Frequently Asked Questions

KSeF API requires valid authentication token.
Obtain valid KSeF session token using certificate or trusted profile. You can also use Invoice Navigator's automatic Fixer tool to correct this instantly.
Yes, PL-R-004 is a critical error that will cause invoice rejection. It must be fixed before submission.

See Also

🇵🇱

E-Invoicing in Poland

Requirements & common errors

Related Errors

PL-R-003

KSeF submission required

Last updated: 19 January 2026

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