You have created a sales document to a corporate account, which has not VAT Registration Number maintained in its master data. Therefore, you expect the system to consider the sale as a B2C - Business To Customer scenario and derive the taxes accordingly to private person transaction. However, the transaction is being taxed as a B2B - Business to Business sale.
SAP Business ByDesign.
Checking if the transaction is a B2B or B2C based on VAT number was an old criteria used by the system. As per the current design, B2B and B2C scenarios are checked based on the type of account.
You need to use Corporate Account type for B2B scenario and Private account type for B2C scenario.
The accounts types can be checked via Business Partner Data -> Buiness Partner. Under the Details section, refer to the Business Partner Roles for the selected business partner.
Business Partner. Taxation. Tax Code. Sales Order. Customer Invoice. Taxes. , KBA , AP-TTE-TC , Tax Calculation , How To