# DT-CIUS-PT-108

Source: https://xmlvalid.com/rules/DT-CIUS-PT-108

> The BT-121 does not meet the defined format: alphanumeric with size between 1 and 5.

- Level: error
- Rule sets: CIUS-PT rules (Portugal, UBL) 2.1.1
- Context: `//ubl:Invoice/cac:TaxTotal/cac:TaxSubtotal/cac:TaxCategory/cbc:TaxExemptionReasonCode | //cn:CreditNote/cac:TaxTotal/cac:TaxSubtotal/cac:TaxCategory/cbc:TaxExemptionReasonCode`
- Test: `matches(.,'^(.{1,5})$')`

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