/*/cac:TaxTotal/cac:TaxSubtotal/cac:TaxCategory[normalize-space(cbc:ID) = 'AE'][cac:TaxScheme/normalize-space(upper-case(cbc:ID))='VAT'][BR-AE-08]-In a VAT breakdown (BG-23) where the VAT category code (BT-118) is "Reverse charge" the VAT category taxable amount (BT-116) shall equal the sum of Invoice line net amounts (BT-131) minus the sum of Document level allowance amounts (BT-92) plus the sum of Document level charge amounts (BT-99) where the VAT category codes (BT-151, BT-95, BT-102) are "Reverse charge".
Hitting this rule in production? Paste the invoice into the validator or wire the API into CI so it never ships broken again.