These fields are shown when direct billing is selected as a payment method on a booking created for corporate travelers.
Client case matter and Charge code are defined by Corporate Company to represent its different transport options or service types for easy expense management.
For example: Client case matter 001 is used for work, 002 is for family.
"Client case" and "Charge code" both are used as business identifiable information. Fleets can check the information recorded in Reports section.