errorPOLKSeF

KSEF-003:Invoice number sequence gap

Invoice numbers must be sequential without gaps within each calendar year. KSeF rejects invoices with numbering gaps or duplicates.

Fix this in your source system

MANUAL

KSeF requires sequential invoice numbers without gaps within each calendar year. This is a numbering policy enforced by your source system. Review your invoice numbering sequence and address any gaps before submitting to KSeF.

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

How to Fix It

Code Example

<NumerFaktury>FV/2026/00001</NumerFaktury>

Common Causes

  • Multiple systems using same number series
  • Cancelled invoices leaving gaps
  • Database restore issues

Frequently Asked Questions

Invoice numbers must be sequential without gaps within each calendar year. KSeF rejects invoices with numbering gaps or duplicates.
Ensure continuous sequential numbering per year. You can also use Invoice Navigator's automatic Fixer tool to correct this instantly.
Yes, KSEF-003 is a critical error that will cause invoice rejection. It must be fixed before submission to ensure your invoice is accepted by the recipient's system.
Many instances of KSEF-003 can be automatically corrected using Invoice Navigator's Fixer tool. Upload your invoice and the tool will identify and fix common issues, including invoice number sequence gap.

Last updated: 19 January 2026

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