{
  "id": "UBL-SR-13",
  "country": "EU",
  "syntax": "ubl",
  "group": "syntax",
  "severity": "fatal",
  "severity_note": "fatal, from the Flag column of the Peppol BIS Billing 3.0 UBL rules index retrieved 2026-10-18.",
  "spec": "Peppol BIS Billing 3.0, May 2026 release, EN 16931 model bound to UBL",
  "statement": "Seller tax registration shall occur maximum once",
  "statement_lang": "en",
  "context": "/ubl:Invoice | /cn:CreditNote",
  "test": "(count(cac:AccountingSupplierParty/cac:Party/cac:PartyTaxScheme[cac:TaxScheme/upper-case(cbc:ID)!='VAT']/cbc:CompanyID) <= 1)",
  "meaning": "The seller tax registration shall occur at most once. The statement has no period and says shall. It does not say identifier. The flag is fatal. The context is the same string as BR-CO-18. The published test counts seller tax-scheme company identifiers whose scheme is not VAT. The scheme comparison is upper-case(cbc:ID)!='VAT' with a straight quote and no space around !=. The count comparison has a space before <= and a space after it.",
  "fix": "Send at most one seller tax registration whose scheme is not VAT.",
  "example_fail": "The seller has two tax registrations whose scheme is not VAT.",
  "example_pass": "The seller has one tax registration whose scheme is not VAT, or none.",
  "example_note": "Illustration of the condition in the official statement. Not an example published by the source.",
  "source_url": "https://docs.peppol.eu/poacc/billing/3.0/rules/ubl-tc434/UBL-SR-13/",
  "source_retrieved": "2026-10-18",
  "last_verified": "2026-10-18"
}