ADV-IBAN: data quality hint
IBAN with spaces or hyphens, the wrong length or wrong check digits
A data quality hint, not part of the official rules. EN 16931, Peppol BIS, XRechnung and Factur-X have no such rule, so an invoice with this hint can be valid. The validator lists hints in a separate section of the result (and in advisories in the API); they never make an invoice invalid.
What this rule checks
Checks the Payment account identifier (BT-84) and the Debited account identifier (BT-91) when they look like an IBAN (two letters of a country that has IBANs, then two digits): UBL cac:PayeeFinancialAccount/cbc:ID and cac:PaymentMandate/cac:PayerFinancialAccount/cbc:ID under any payment means code, and CII ram:IBANID. Other account numbers, such as a Swedish Bankgiro, are not checked. ISO 13616 writes the IBAN without spaces or hyphens in electronic form, with a fixed length per country and check digits that pass the mod 97 test. The official rules do not check the IBAN, except KoSIT BR-DE-19/20 and Peppol DE-R-019/020 for German invoices; where one of them reports an account, it gets no hint.
How to fix it
Write the IBAN without spaces or hyphens (e.g. BE71096123456769) and compare it with the account details from the bank.
Related rules
Check your invoice
Upload your invoice to check it against the official EN 16931, Peppol BIS, XRechnung or Factur-X rules. The result lists data quality hints such as ADV-IBAN in a separate section; they never make an invoice invalid. Free, instant, no signup.