Only visible for staff users (users with level 20+), inside the order entry template.
About
Charges for Invoicing are used by staff users for calculating costs and charges of an entered order.
When an order consists of splitted shipments, Charges for Invoicing is only be visible for the main order (so called .00-order). If you need Charges for Invoicing also for sub shipments, then send Cargo Office Programmers a request.
For staff users a totalisation of billed items is given inside Active Shipments.
You are able to maintain your invoicing items through products overview.