Norwegian Tax Authority, Skatteetaten, requires that an internal sales tax codes mapped to valid standard tax code while generating SAF-T file from D365FO. Ref. to Skatteetaten, The internal VAT tax codes must be mapped to the corresponding Norwegian SAF-T Standard VAT codes in schema location MasterFiles.In situations when mapping is not possible, please use “NA” as value for . Note that the must be rendered exactly as in the code list. Example: The Standard Tax Code for
Input VAT deductible (domestic) is "1" and not "01" or "001" (https://www.skatteetaten.no/globalassets/bedrift-og-organisasjon/starte-og-drive/rutiner-regnskap-og-kassasystem/saf-t-regnskap/norwegian-saf-t-financial-data---technical-description2.pdf)

If a user doesn't map an internal sales tax codes mapped to a standard tax code, she will get “NA” as standard code that will not be accepted by the tax authority.
Therefore, it would be required that Microsoft add a validation rule for SAF-T (NO) report so that the users get a warning/notification of internal sales tax code lacking mapping in the solution.