UBL-SR-20: Payee identifier shall occur maximum once, if the Payee is different from the Seller

The rule applies to each cac:PayeeParty. The message says the Payee identifier may occur at most once when the Payee is different from the Seller, but the test also requires the PayeeParty's cac:PartyName/cbc:Name to be different from the Seller's cac:AccountingSupplierParty/cac:Party/cac:PartyLegalEntity/cbc:RegistrationName for the rule to pass. In addition, the test requires that among cac:PartyIdentification/cbc:ID elements in the PayeeParty, at most one has a @schemeID that is not SEPA (case-insensitive); identifiers with @schemeID equal to SEPA are not counted. A document fails if a PayeeParty contains more than one non-SEPA identifier, if the PayeeParty's name equals the supplier's registration name, or if the PayeeParty has no cac:PartyName/cbc:Name, because an empty name never compares as different.

Ensure that each cac:PayeeParty has at most one cac:PartyIdentification/cbc:ID whose @schemeID is not SEPA (case-insensitive). If there are multiple, remove or change the extra identifiers so that only one non-SEPA identifier remains. Also make sure the cac:PartyName/cbc:Name in the PayeeParty is not identical to the supplier's cac:AccountingSupplierParty/cac:Party/cac:PartyLegalEntity/cbc:RegistrationName. If the payee is actually the same as the seller, omit the cac:PayeeParty entirely.