# DT-CIUS-PT-011

Source: https://xmlvalid.com/rules/DT-CIUS-PT-011

> The BT-12 does not meet the defined format: alphanumeric with size between 1 and 20.

- Level: error
- Rule sets: CIUS-PT rules (Portugal, UBL) 2.1.1
- Context: `//ubl:Invoice/cac:ContractDocumentReference/cbc:ID | //cn:CreditNote/cac:ContractDocumentReference/cbc:ID`
- Test: `matches(.,'^(.{1,20})$')`

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