BR-O-10 A not-subject-to-VAT breakdown must give the matching exemption reason

"vatExemptionReasons": { "O": "Not subject to VAT" }

{
  "rule": "BR-O-10",
  "field": [
    "BT-120",
    "BT-121"
  ],
  "severity": "fatal",
  "message": "The VAT breakdown for category O (Not subject to VAT) must have a VAT exemption reason code (BT-121) meaning \"Not subject to VAT\", or the VAT exemption reason text (BT-120) \"Not subject to VAT\" (or the equivalent standard text in another language). You set vatExemptionReasons.O to an empty value, which suppresses the wording this library would otherwise supply. The reason is what tells the buyer — and their auditor — why an invoice line carries no VAT; a zero with no explanation is indistinguishable from a mistake.",
  "fix": "Either remove vatExemptionReasons.O entirely, in which case this library supplies the standard text \"Not subject to VAT\", or set it to your own wording in the invoice language.",
  "example": "\"vatExemptionReasons\": { \"O\": \"Not subject to VAT\" }",
  "xpath": "/ubl:Invoice/cac:TaxTotal/cac:TaxSubtotal/cac:TaxCategory/cbc:TaxExemptionReason",
  "docsUrl": "https://attestwire.com/rules/BR-O-10"
}