# ibr-029

Source: https://xmlvalid.com/rules/ibr-029

> If both Invoicing period start date (ibt-073) and Invoicing period end date (ibt-074) are given then the Invoicing period end date (ibt-074) MUST be later or equal to the Invoicing period start date (ibt-073).

- Level: error
- Rule sets: PINT Billing rules 1.1.3, PINT Billing rules (as shipped with PINT AE) 1.0.4
- Context: `cac:InvoicePeriod`
- Test: `(exists(cbc:EndDate) and exists(cbc:StartDate) and xs:date(cbc:EndDate) >= xs:date(cbc:StartDate)) or not(exists(cbc:StartDate)) or not(exists(cbc:EndDate))`

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