Issue:

A Client's default Tax Area is stored on the Client record. For example, MD for Maryland. Orders to this customer are now need to be shipped as non-taxable as the Products are intended for resale. The tax area field of the Client's record has been updated to reflect this but new orders are still showing MD as the default Tax Area.

Solution:

A Tax Area stored on a default Ship To record will overrule the Tax Area stored on the Client record. Check the Ship To records associated with this Client and ensure that these records show the intended Tax Area.