# ibr-090

Source: https://xmlvalid.com/rules/ibr-090

> Only one project reference (ibt-011) is allowed on document level.

- 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:ProjectReference) <= 1) and (count(cac:AdditionalDocumentReference[cbc:DocumentTypeCode='50']) <= 1)`

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