The tax amount per category MUST be the taxable amount multiplied by the category percentage.
/ubl:CreditNote/cac:TaxTotal/cac:TaxSubtotal((cbc:TaxableAmount) and (cac:TaxCategory/cbc:Percent) and (xs:decimal(cbc:TaxAmount - 1) < xs:decimal(cbc:TaxableAmount * (xs:decimal(cac:TaxCategory/cbc:Percent) div 100))) and (xs:decimal(cbc:TaxAmount + 1) > xs:decimal(cbc:TaxableAmount * (xs:decimal(cac:TaxCategory/cbc:Percent) div 100)))) or not(cac:TaxCategory/cbc:Percent) or not(cbc:TaxableAmount)