To set up your tax rates,

1. Navigate to Admin > Invoices - Tax Rates.
   
2. Click New Tax Rate to add a new one, or click an existing rate's name or pencil icon to edit it.
   WARNING: Unless you have never used a rate you wish to edit, editing an existing rate can corrupt existing invoices and cause other problems. We strongly recommend creating a new rate and using that instead.
3. Enter the Name and percentage Amount.
   
4. If you have multiple tax rates enabled, check Is tax group if this is a combination of multiple rates. See multiple tax rates for more info.
5. If you have a QuickBooks or Xero integration, click the QuickBooks or Xero dropdown and select its corresponding tax rate.
6. When finished, click Create Tax rate or Update Tax rate.

The first one in the list will be the default. You can re-order these by clicking and dragging using the "hamburger" (three lines) on the far right.