{
  "id": "UBL-SR-36",
  "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": "Invoice line period shall occur maximum once",
  "statement_lang": "en",
  "context": "cac:InvoiceLine | cac:CreditNoteLine",
  "test": "(count(cac:InvoicePeriod) <= 1)",
  "meaning": "The invoice line period shall occur at most once. The statement has no period and says shall. It is 44 characters. The flag is fatal. The context is an invoice line or a credit note line. The published test counts cac:InvoicePeriod. That test string is the same as UBL-SR-08. The count comparison has a space before <= and a space after it.",
  "fix": "On an invoice line or a credit note line, send at most one invoice period.",
  "example_fail": "An invoice line has two invoice periods.",
  "example_pass": "An invoice line has one invoice period, 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-36/",
  "source_retrieved": "2026-10-18",
  "last_verified": "2026-10-18"
}