BR-AE-01
This id stands for 2 different rules, one per rule set below: Factur-X numbers its rules in each profile separately.
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.
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 "Reverse charge" shall contain in the VAT Breakdown (BG-23) exactly one VAT category code (BT-118) equal with "VAT reverse charge".
/ubl:Invoice | /cn:CreditNote
((exists(//cac:TaxCategory[cac:TaxScheme/normalize-space(upper-case(cbc:ID))='VAT']/cbc:ID[normalize-space(.) = 'AE']) or exists(//cac:ClassifiedTaxCategory[cac:TaxScheme/normalize-space(upper-case(cbc:ID))='VAT']/cbc:ID[normalize-space(.) = 'AE'])) and (count(cac:TaxTotal/cac:TaxSubtotal/cac:TaxCategory[cac:TaxScheme/normalize-space(upper-case(cbc:ID))='VAT']/cbc:ID[normalize-space(.) = 'AE']) = 1)) or (not(//cac:TaxCategory[cac:TaxScheme/normalize-space(upper-case(cbc:ID))='VAT']/cbc:ID[normalize-space(.) = 'AE']) and not(//cac:ClassifiedTaxCategory[cac:TaxScheme/normalize-space(upper-case(cbc:ID))='VAT']/cbc:ID[normalize-space(.) = 'AE']))
Checked with EN 16931 Invoice (UBL), EN 16931 Credit Note (UBL), Croatia eRačun Invoice (UBL), Croatia eRačun Credit Note (UBL)
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 "Reverse charge" shall contain in the VAT breakdown (BG-23) exactly one VAT category code (BT-118) equal with "VAT reverse charge".
/rsm:CrossIndustryInvoice
(count(//ram:ApplicableHeaderTradeSettlement/ram:ApplicableTradeTax[ram:CategoryCode='AE'])=0 and count(//ram:SpecifiedLineTradeSettlement/ram:ApplicableTradeTax[ram:CategoryCode='AE'])=0 and count(//ram:CategoryTradeTax[ram:CategoryCode='AE'])=0) or ( count(//ram:ApplicableHeaderTradeSettlement/ram:ApplicableTradeTax[ram:CategoryCode='AE'])=1 and (exists(//ram:SpecifiedLineTradeSettlement/ram:ApplicableTradeTax[ram:CategoryCode='AE']) or exists(//ram:CategoryTradeTax[ram:CategoryCode='AE'])))
Checked with EN 16931 Invoice (CII)