If you want to set your sales taxes, go to the Settings ➝ Taxes. Here you can add Taxes or Tax Groups that you will use on Invoices, Taxes, and Items.
You can even set one of the taxes as default, so each time you will create an item or a task, this tax will be chosen by default.
In case you don’t pick a default tax, the tax field available on tasks/items will stay empty.
What is a Tax Group? How do I create it?
You can create a Tax Group if you use more then one sales tax for your products.
To create Tax Group go to, Settings ➝ Taxes ➝ Add New Tax Group
Note: When you create a new product or task you will be able to assign a tax group for it.
You will also be able to add a grouped taxes amount to the product cost when you raise an invoice or estimate.