
Originally Posted by
lhungil
You are correct (and thank you for mentioning this in the support thread)!
Background / Why
The "tax" field is pulled from the Zen Cart "tax" rate for the product. This does not include any "local sales tax" calculations. The "Local Sales Tax" mod does not modify what is shown in this field (admin side). It also does not include changes to any templates (customer side). Showing a combined rate may be considered in the future (the value in the database saved with the product should not be altered). If you (or anyone else) tackles this project, please submit the changes / patches to this support thread!
Modifying the value of this field using "Edit Orders" will only modify the Zen Cart tax rate, not any "local sales tax" calculations. "Edit Orders" does not support manually changing the "local sales tax" rate for products. Any "local sales tax" will be applied in addition to the rate listed in this field. Adding the ability to modify the "local sales tax" order line will not be considered for "Edit Orders" in the future (unless an overwhelming need with no workaround is found - as this would require substantial modification to both modules).
Temporary Workaround / Hide the field
If you are concerned with the rate being shown to people using the Zen Cart admin interface, remove the column from showing in "/admin/orders.php" and "/admin/invoice.php" (I typically just alter the invoice and teach clients to always use this button to display / print their invoices).
For the customer side, this field is only shown on the account history page if products with different tax rates are in the same order. If you might encounter this situation you can edit "/includes/templates/YOUR_THEME_NAME/templates/tpl_account_history_info_default.php" to remove the tax column from being shown.