In a scenario where Bill-to and Ship-to addresses are different from the Account's, the Customer's Tax Registration number is not the one expected.
The Ship-to and Bill-to Address is from country B and the Account is from country A.
You want the Customer's Tax Registration Number to reflect Country B but Country A is retrieved (A and B stands for the respective countries' names).
SAP Business ByDesign
Reproducing the Issue
Go to the Sales Order Work Center.
Go to the Sales Order View.
Search for Sales Order YYY and select it (YYY is the ID of the Sales Order).
Click Edit, stay on the General Tab.
The Account name is Customer AA from Country A.
The Bill-to and Ship-to address is for Customer BB from Country B.
(Customers AA and BB are the respective names for the Account and Bill-to Parties)
Go to the Items tab.
Navigate to the Taxes subtab.
Check The Customer's Tax Registration section.
The Country maintained is Country A.
The Tax Number is for Customer AA that is, the Account determined on the Sales Order.
The Customer's Tax Registration information is pulled from the Account Financial Data.
This is the expected system behavior.
For more information on how the Tax Number is determined across documents, please check Knowledge Base Article 1914897
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