# BR-CIUS-PT-01

Source: https://xmlvalid.com/rules/BR-CIUS-PT-01

> An Invoice shall contain the Seller VAT identifier (BT-31).

- Level: error
- Rule sets: CIUS-PT rules (Portugal, UBL) 2.1.1
- Context: `//ubl:Invoice | //cn:CreditNote`
- Test: `exists(cac:AccountingSupplierParty/cac:Party/cac:PartyTaxScheme/cbc:CompanyID)`

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