Billing groups can be used to separate your customers into different groups for billing purposes.
Customizing billing groups
Go to Invoices on the top of the order panel. In the popup window that appears, go to Settings on the left. Another popup window will appear and there will be a list of billing groups that can be edited on the top right of that window.
Assigning billing groups
Go to Customers on the top of the order panel. Double-click on a customer to edit them. There is a dropdown menu for which billing group the customer is assigned to on the right side, near the top.
Using billing groups
Go to Invoices on the top of the order panel. When running Customer Invoices or Quickbooks invoicing on the left, you can select which billing group to run invoices for.