FX-SCH-A-000256
An Invoice that contains an Invoice line (BG-25), a Document level allowance (BG-20) or a Document level charge (BG-21) where the VAT category code (BT-151, BT-95 or BT-102) is “Exempt from VAT” shall contain exactly one VAT breakdown (BG-23) with the VAT category code (BT-118) equal to "Exempt from VAT".
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.
[BR-E-01] An Invoice that contains an Invoice line (BG-25), a Document level allowance (BG-20) or a Document level charge (BG-21) where the VAT category code (BT-151, BT-95 or BT-102) is “Exempt from VAT” shall contain exactly one VAT breakdown (BG-23) with the VAT category code (BT-118) equal to "Exempt from VAT".
/rsm:CrossIndustryInvoice
(count(//ram:ApplicableHeaderTradeSettlement/ram:ApplicableTradeTax[ram:CategoryCode='E'])=0 and count(//ram:SpecifiedLineTradeSettlement/ram:ApplicableTradeTax[ram:CategoryCode='E'])=0 and count(//ram:CategoryTradeTax[ram:CategoryCode='E'])=0) or ( count(//ram:ApplicableHeaderTradeSettlement/ram:ApplicableTradeTax[ram:CategoryCode='E'])=1 and (exists(//ram:SpecifiedLineTradeSettlement/ram:ApplicableTradeTax[ram:CategoryCode='E']) or exists(//ram:CategoryTradeTax[ram:CategoryCode='E'])))
Checked with Factur-X / ZUGFeRD BASIC