If the tab says Bill Engagements or Bill Projects, select the parent and subsidiary clients individually for the project(s) or engagement(s) you would like to bill and skip the next two steps. If you have
Automatically select subsidiary clients when selecting parent Clients
selected in the Billing tab of the User Preferences dialog, select the engagements or projects for the parent client you want to bill and the application will automatically select the same engagements or projects for the subsidiary clients.