INVALID_BANK_ACCOUNT_FORMAT: Polish bank account (NrRB) must be 28 characters for IBAN…

StandardKSeF FA(3), Polish national e-invoicing systemSeverityError: the invoice is rejectedSyntaxFA(3) XMLApplies toStructured invoices (FA(3) schema) submitted to the Polish KSeF. XSD codes come from the schema, semantic codes from the Ministry of Finance information sheet; KSeF rejects invoices that fail an error-level rule.

Official rule text

[INVALID_BANK_ACCOUNT_FORMAT] Polish bank account (NrRB) must be 28 characters for IBAN format (PL + 26 digits) or 26 digits for NRB format

Why this error occurs

KSeF checks the FA(3) XML in two stages: XSD schema (structure, element order, data types, patterns such as NIP or dates) and semantic rules from the Ministry of Finance information sheet (consistency of amounts, annotations P_16 to P_23, roles of Podmiot2/Podmiot3, bank account formats, currency rates).

How to fix it

Fix the element named in the message. For XSD errors compare the element order and value pattern with the FA(3) schema; for semantic errors apply the cause and fix hints listed on this page. Re-validate before submitting to KSeF: a rejected invoice has no KSeF number and is not issued.

What the validator checks

Check levelsemantic / format

Typical causes

Incorrect Polish IBAN format
Wrong number of digits in bank account
Missing or malformed IBAN prefix

Check your invoice

Drop your XML or PDF on the validator and every failed rule is linked to its page here. Free, no account, the file is not stored.

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Same check via API:

curl -F file=@invoice.xml https://einvoicechecker.com/v1/validate

Related rules

AMOUNT_NO_SEPARATORS Amount fields must not contain spaces, commas, or any non-numeric characters except…
DECIMAL_PRECISION Amount field exceeds maximum decimal precision defined in §2.6 of FA(3) specification
GTU_FORMAT GTU value must match pattern GTU_XX (GTU_01 through GTU_13)
IPKSEF_FORMAT IPKSeF must be exactly 13 alphanumeric characters [0-9a-zA-Z] (§12.1)
NRRB_LENGTH NrRB must be 10–34 characters (§12.1)

Frequently asked questions

What does INVALID_BANK_ACCOUNT_FORMAT mean?

INVALID_BANK_ACCOUNT_FORMAT is a ksef fa(3) rule: Polish bank account (NrRB) must be 28 characters for IBAN format (PL + 26 digits) or 26 digits for NRB format

Will my invoice be rejected because of INVALID_BANK_ACCOUNT_FORMAT?

Yes. INVALID_BANK_ACCOUNT_FORMAT is flagged "fatal"; validators (KoSIT, Peppol access points, the German ZRE/OZG-RE portals, KSeF) reject the invoice until it is fixed.

Which formats does INVALID_BANK_ACCOUNT_FORMAT apply to?

Structured invoices (FA(3) schema) submitted to the Polish KSeF. XSD codes come from the schema, semantic codes from the Ministry of Finance information sheet; KSeF rejects invoices that fail an error-level rule. Syntax: FA3.

Source: KSeF FA(3) schema 1-0E + semantic rules (@ksefuj/validator 0.4). Catalogue generated from the official rule sets on 2026-10-15.

INVALID_BANK_ACCOUNT_FORMAT: Polish bank account (NrRB) must be 28 characters for IBAN format (PL + 26 digits) or…