KSEF-001
Error Guide
🇵🇱 KSEF-001: NIP validation failed in Poland
ErrorMandatoryNeeds Input
Polish NIP (tax identification number) must be 10 digits with valid checksum. Both seller and buyer NIP are required for B2B invoices. Leading zeros are significant.
Quick Facts
Severity
Error (rejection)
Ruleset
KSeF
Mandate
B2B Mandatory
Fix Type
Needs input
Why This Matters in Poland
Poland requires e-invoicing using KSeF XML format. Invoices with this error will be rejected. They cannot be processed for Poland compliance.
Invoice Navigator covers 134 KSeF FA(2) rules for Poland. Auto-remediates 78% of top rejection errors.
How to Fix KSEF-001
Poland E-Invoicing Requirements
Phase
Status
Scope
KSeF voluntary
Live (Jan 2022)
All VAT payers (opt-in)
B2B mandatory
Live (Feb 2026)
All Polish VAT payers
B2G
Live (Feb 2026)
Included in general KSeF mandate
Common Causes
- •NIP entered with only 9 digits
- •Invalid checksum
- •NIP cancelled or inactive
Fix KSEF-001 automatically
Upload your invoice and let Invoice Navigator auto-remediate this error.