{
  "id": "UBL-SR-08",
  "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 period shall occur maximum once",
  "statement_lang": "en",
  "context": "/ubl:Invoice | /cn:CreditNote",
  "test": "(count(cac:InvoicePeriod) <= 1)",
  "meaning": "The invoice period shall occur at most once. The statement has no period, says shall, and is shorter than 40 characters. The flag is fatal. The context is the same string as BR-CO-18. The published test is (count(cac:InvoicePeriod) <= 1). The comparison has a space before <= and a space after it.",
  "fix": "Send at most one invoice period.",
  "example_fail": "The invoice has two invoice periods.",
  "example_pass": "The invoice 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-08/",
  "source_retrieved": "2026-10-18",
  "last_verified": "2026-10-18"
}