# BR-CIUS-PT-53

Source: https://xmlvalid.com/rules/BR-CIUS-PT-53

> The Item Buyer's identifier (BT-156) shall be filled.

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

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