Message

Value MUST be part of code list 'VAT date code (UNCL2005 subset)'.

Context
/ubl:Invoice/cac:InvoicePeriod/cbc:DescriptionCode
Test
(some $code in $clUNCL2005 satisfies $code = normalize-space(text()))
Code lists
VAT date code (UNCL2005 subset)
Usage
/ ubl:Invoice / cac:InvoicePeriod / cbc:DescriptionCode