{
  "id": "BR-CO-20",
  "country": "EU",
  "syntax": "ubl",
  "group": "document",
  "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": "If Invoice line period (BG-26) is used, the Invoice line period start date (BT-134) or the Invoice line period end date (BT-135) shall be filled, or both.",
  "statement_lang": "en",
  "context": "cac:InvoiceLine/cac:InvoicePeriod | cac:CreditNoteLine/cac:InvoicePeriod",
  "test": "exists(cbc:StartDate) or exists(cbc:EndDate)",
  "meaning": "If an invoice line period (BG-26) is used, the invoice line period start date (BT-134) or the invoice line period end date (BT-135) must be filled, or both. The statement ends with a period. The context is the invoice line period or the credit note line period, with spaces around the bar. The published test is exists on the start date or exists on the end date. It has no description-code branch and it does not compare the two dates.",
  "fix": "When an invoice line period is present, send the start date (BT-134), the end date (BT-135), or both.",
  "example_fail": "An invoice line period has neither a start date nor an end date.",
  "example_pass": "An invoice line period has an end date and no start date.",
  "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/BR-CO-20/",
  "source_retrieved": "2026-10-18",
  "last_verified": "2026-10-18"
}