Validator

🇵🇱 Validate KSeF Invoices for Poland

KSeFMandatory

KSeF (FA(3)) is required in Poland. Poland launched KSeF (Krajowy System e-Faktur) as mandatory for all B2B transactions on February 1, 2026.

Quick Facts

Format

KSeF (FA(3))

Mandate

B2B Mandatory

Peppol

Not connected

Portal

KSeF ↗

What We Validate

FA(3) XSD schema compliance

NIP (tax number) format and checksum validation

Mandatory header fields (Naglowek) completeness

Seller (Podmiot1) identification and NIP presence

Buyer (Podmiot2) identification and NIP/PESEL format

Invoice date (P_1) not in the future

Invoice number (P_2) uniqueness structure

VAT rate and amount calculation consistency

RodzajFaktury (invoice type) enumeration values

Duplicate detection (NIP + invoice type + number)

Invoice Navigator covers 134 KSeF FA(2) rules for Poland. Auto-remediates 78% of top rejection errors.

Common KSeF Errors

#1XSD-001XML not conforming to FA(3) schemaFix guide

#2440Duplicate invoice detected (NIP + type + number)Fix guide

#3XSD-NIPInvalid NIP format or checksum failureFix guide

#4XSD-P1Invoice date (P_1) is in the futureFix guide

#5XSD-REQMissing mandatory field in Fa sectionFix guide

#621405Input data validation error (invalid payload)Fix guide

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

Validation engineKSeF (centralized government validation)

Required CIUSKSeF XML schema (FA(2) — proprietary, not EN 16931)

Government portalKSeF (ksef.mf.gov.pl)

Routing identifierNIP (tax identification number)

PeppolNo — KSeF is a closed national system

KSeF is architecturally different from Peppol-based mandates. If you've built for Belgium or Germany, assume nothing transfers.

FAQ

What is KSeF?

KSeF (Krajowy System e-Faktur) is Poland's National e-Invoice System. From February 2026, all B2B invoices must be submitted as structured XML through KSeF. The system validates each invoice against the FA(3) schema and assigns a unique KSeF ID.

What is the FA(3) schema?

FA(3) is the latest version of Poland's structured invoice schema, replacing FA(2) from February 2026. It defines over 300 fields — some always mandatory, others conditional on transaction type. The XML must conform to the official XSD published by the Ministry of Finance.

How does KSeF validate NIP numbers?

NIP is a 10-digit Polish tax identification number. KSeF validates the format and mod-11 checksum (weights: 6-5-7-2-3-4-5-6-7). The seller's NIP is mandatory — without it, the invoice cannot be issued. The buyer's NIP determines whether the invoice appears in their KSeF account.

When does the KSeF mandate take effect?

February 1, 2026 for large taxpayers (over PLN 200 million annual turnover). April 1, 2026 for all other VAT-registered entities. January 1, 2027 for micro-entrepreneurs with monthly sales under PLN 10,000.

Is this validator free?

Yes. You can validate up to 10 invoices per month for free. No signup required for basic validation.

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What We Validate

FA(3) XSD schema compliance

NIP (tax number) format and checksum validation

Mandatory header fields (Naglowek) completeness

Seller (Podmiot1) identification and NIP presence

Buyer (Podmiot2) identification and NIP/PESEL format

Invoice date (P_1) not in the future

Invoice number (P_2) uniqueness structure

VAT rate and amount calculation consistency

RodzajFaktury (invoice type) enumeration values

Duplicate detection (NIP + invoice type + number)

Invoice Navigator covers 134 KSeF FA(2) rules for Poland. Auto-remediates 78% of top rejection errors.

Common KSeF Errors

#1XSD-001XML not conforming to FA(3) schemaFix guide

#2440Duplicate invoice detected (NIP + type + number)Fix guide

#3XSD-NIPInvalid NIP format or checksum failureFix guide

#4XSD-P1Invoice date (P_1) is in the futureFix guide

#5XSD-REQMissing mandatory field in Fa sectionFix guide

#621405Input data validation error (invalid payload)Fix guide

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

Validation engineKSeF (centralized government validation)

Required CIUSKSeF XML schema (FA(2) — proprietary, not EN 16931)

Government portalKSeF (ksef.mf.gov.pl)

Routing identifierNIP (tax identification number)

PeppolNo — KSeF is a closed national system

KSeF is architecturally different from Peppol-based mandates. If you've built for Belgium or Germany, assume nothing transfers.

FAQ

What is KSeF?

What is the FA(3) schema?

How does KSeF validate NIP numbers?

When does the KSeF mandate take effect?

Is this validator free?

Yes. You can validate up to 10 invoices per month for free. No signup required for basic validation.