To charge for shipping, consultation, design, and other services, our customers usually use the following approach:
Create a new regular stock item "delivery" (as procured), quantity 100000 (any big), cost zero (or your real cost, see below).
Choose the unit of measure, for example, km, hour, etc.
Add this item to customer orders and/or invoices with your real price.
For separating these items from inventory items, please create a separate product group.
In this way:
You will be able to charge your customers and get statistics of provided services during a period from item reports.
If the item has a cost (for example, shipping that you order from a vendor of yours), this allows linking customer orders with purchase orders and thus allocating costs towards particular customer orders
About an alternative option read here.