phpListings allows tax rates to be applied to listing invoices. Inclusive, exclusive and compound tax rate types are supported with an ability to link a tax rate to a user location.
Tax rates can be managed under "Administrator - Settings - Tax Rates".
Linking Tax Rate to a Location.
When adding a tax rate you can select a location for that tax to be applied to.
Account location setting is considered to be a user location for taxing.
Global tax rates (rates with no location selected) are applied to all locations.
If you have a tax rate set for the state and a city in that state then the city tax rate will be applied because of higher priority.
Compound Tax Rate.
If the tax rate is set as compound it will be applied to the total that includes the previouly calculated tax amount.
For example, the subtotal for the invoice is $100. After applying the 20% VAT tax the total becomes $120 and is used as a new base subtotal value for the compound tax rate calculation.
Product Price: $100
Compound Tax: 10%
Total Tax = (100 * 0.2) + ((100 * 0.2 + 100) * 0.1) = $32
Inclusive / Exclusive Tax Rate.
You can set the global tax type to use under "Administrator - Settings - Settings - Billing - Tax Type".
Use the "Inclusive" tax type if you want the tax amount to be included into the total amount. E.g.: if the product price is $50 and the inclusive tax is 20%, the invoice total will be $50 and the tax of $10 will be deducted from the product price.
If the "Exclusive" tax type is used the tax amount is added to the subtotal. For example, if your product price is $50 and the tax value is 20% the total will be $60 because we add the tax amount of $10 to the product price.
Tax Exempt Users.
You can disable all tax rates for the user by enabling the "Tax Exempt" setting for that account under "Administrator - Users - Users".