There is sometimes confusion with the setup of state specific tax rates with osCommerce. For instance if you are charging state taxes shipped within state for such states as Ohio (OH) or California (CA) then you need to assure that a few settings are correctly configured.
The primary issue is that even after setting up the correct tax zones, classes, and rates the sales tax does not appear to apply when purchasing from a state for which the tax zone is configured. I found after some research that the following settings must be configured correctly. Without assuring the following steps are followed your sales tax behavior may not work as expected:
- first setup your Tax Zones, Tax Classes, and Tax Rates
- assure each product has a Tax Class and Products Weight
- at Configuration switch Display Prices with Tax to false.
By making sure that the settings mentioned above are set correctly your state specific tax rates should be working.