In order to do batch billing you need to setup your billing preferences. You can setup any number of billing preferences and then associate them with the appropriate action types.
The billing preferences govern which invoice layout should be used and how the line items and headings are arranged.
To get to the billing preferences page, go to Admin > Billing > Billing Preferences.
You will then see the page in the screenshot below.
Step 1: Go to the Workflow Admin area
Step 2: Click on the Action Type that you want to edit
(In the example screenshot below, the "Criminal Litigation" workflow type has been selected)
Step 3:
1) Click on 'Edit Action Type'
2) Select your Default Billing Preference from the drop down list
3) Click 'Save'