{
  "id": "UBL-SR-28",
  "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": "Mandate reference identifier shall occur maximum once",
  "statement_lang": "en",
  "context": "cac:PaymentMeans",
  "test": "(count(cac:PaymentMandate/cbc:ID) <= 1)",
  "meaning": "The mandate reference identifier shall occur at most once. The statement has no period, says shall, and says identifier. It is 53 characters. The flag is fatal. The context is cac:PaymentMeans. The published test counts the payment mandate identifier. The comparison has a space before <= and a space after it.",
  "fix": "Send at most one payment mandate identifier.",
  "example_fail": "The payment means has two payment mandate identifiers.",
  "example_pass": "The payment means has one payment mandate identifier, 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-28/",
  "source_retrieved": "2026-10-18",
  "last_verified": "2026-10-18"
}