In your store's Admin area, go Go to the System > Localization > Tax Classes→ Localization → Tax classes
By default, AbanteCart include includes one Product Tax Class: Taxable Goods. If you have different Tax Rules that will apply to storefront, you will want to create Create a new Product Tax Class or Edit Tax Rates for "Taxable Goods" class if required.
When you click to edit Tax Class you will see a list of Tax Rates applied in this Tax Class.
If you plan to reach customers from different geo locations and would like to apply custom tax rates for each location please create required locations in System > → Localization > → Locations.