To set up additional taxes, you need to go to the farmerswife server > Setup > Financial. If adding multiple you can change the order of the taxes on how they should be applied.
In the Contact window, under the "Client Details" tab, you can now select which taxes should apply for that Client. By default, all configured taxes apply!
Projects will inherit the tax from the Client. If an Object is marked taxable, then the checked taxes for the client will apply to those objects when Invoicing. Each tax is applied to the subtotal, they are NOT compounded.
Be sure to modify your invoice and/ or report templates to reflect the additional taxes.
If you later REMOVE the additional Taxes again (select tax, right mouse click > remove), only Invoice in the Invoice Manager will remain untouched. All Projects will have the previous taxes only applied.