There are two ways to add Tax Rates inside the system. The first way is through the System Settings: 

1. Click on Settings, near the bottom of the left hand navigation bar. 

2. Click on Tax Rate, this will be under the "Billing and Invoicing" Section. 

3. Click the "Add Tax Rate" button near the top right of the section. 

4. Add the title of your Tax Rate (Florida Tax, Alabama Tax, etc), and then enter the rate that is equivalent to your desired tax.  Once you have entered both fields, click submit. 

The second way is inside the Billing & Expenses section of a case, more specifically inside each invoice item. 

1. Click the edit icon of the invoice item. 

2. Click the drop down next to "Tax Rate", then select "Add Tax Rate". Once you are done click submit.