# ibr-097

Source: https://xmlvalid.com/rules/ibr-097

> Invoicing period (ibg-14) MUST occur maximum once.

- Level: error
- Rule sets: PINT Billing rules 1.1.3, PINT Billing rules (as shipped with PINT AE) 1.0.4
- Context: `/ubl:Invoice | /cn:CreditNote`
- Test: `(count(cac:InvoicePeriod) <= 1)`

Validate a document against these rules: https://xmlvalid.com/validate