BR-KSA-39
The invoice must contain the seller VAT registration number or seller group VAT registration number (BT-31).
What the rule checks
As the rule set's publisher wrote it. The rule runs on every element the context matches, and fails where the test is false; the validator reports the line of that element.
/ubl:Invoice | /cn:CreditNote
not(((cac:AccountingSupplierParty/cac:Party/cac:PartyTaxScheme/cbc:CompanyID) != '' and (cac:AccountingSupplierParty/cac:Party/cac:PartyTaxScheme/cac:TaxScheme[normalize-space(cbc:ID) = 'VAT'])))
Checked with Saudi Arabia ZATCA Tax Invoice (UBL), Saudi Arabia ZATCA Simplified Tax Invoice (UBL)