Billing Groups
You create billing groups so that you can bill several projects together on one invoice. This feature is useful if you have multiple projects for the same client and the client wants to receive one invoice for all of the projects.
Main Project
If you are billing a client for a set of projects worked on by multiple companies within your enterprise, the company that owns the main project in the billing group is the company that generates the invoice for the entire billing group.
Use the Billing Group List to review a billing group's settings, its main project, and a list of its sub-projects.