# BR-CIUS-PT-29

Source: https://xmlvalid.com/rules/BR-CIUS-PT-29

> The Contract reference (BT-12) shall be filled.

- Level: error
- Rule sets: CIUS-PT rules (Portugal, UBL) 2.1.1
- Context: `cac:ContractDocumentReference`
- Test: `exists(cbc:ID)`

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