3126116 - Tax Code/Classification getting applied to all distribution channels/Sales Area

You have changed the tax classification in one sales organization/plant, but the changes are being applied in all sales organizations and plants. 

SAP S/4HANA Cloud

 When updating the Tax Classification of a Customer for one sales area, this update will apply to all sales areas. 

This is the system behavior. In S/4 HANA Cloud, for the same material, only one tax indicator can exist in each country. For the material tax classification the underlying table has as key fields being Departure Country + Material which means a material classified, for example, Germany will have the same classification in every German plant. The situation is similar for customer tax classification, the underlying table has as key fields Customer + Departure Country + Tax Category so also here, the maintained tax classification is dependent on those three key fields, not on the sales area. 

Although this is a system behavior you might consider the usage of Cloud BAdI to apply a different Tax Classification on Sales Order Header for those cases. Please take into consideration SAP police over Custom Logic on customer systems. 

Creating Custom Logic

Business Add-Ins (BAdIs) for Sales Documents

Custom Logic, Tax Classification , KBA , SD-BF-TX , Taxes , How To