The flow of determining whether to charge tax is:
1. The Sales journal
2. The Revenue account
3. Customer is charged and Geographical Region..
I suspect the problem is within 2 above. The revenue account may be in a sub-folder of Sales/Revenue (NewViews > Account) that the Default trade / Tax Info is set to Exempt for the folder.I suggest that you set it to Taxable and then set the individual revenue accounts for the sub folder to exempt.
When moving items to other accounts and you are prompted to Reprocess or As Is. Choose As Is as the tax amount will be left intact.
Regards to All,