# BR-CIUS-PT-52

Source: https://xmlvalid.com/rules/BR-CIUS-PT-52

> The Invoice line object identifier (BT-128) shall be filled.

- Level: error
- Rule sets: CIUS-PT rules (Portugal, UBL) 2.1.1
- Context: `cac:InvoiceLine | cac:CreditNoteLine`
- Test: `exists(cac:DocumentReference) and not(cac:DocumentReference/cbc:ID)`

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