Additional charges is a method for the store owner to add extra line items to a transaction. These line items can be anything that is required. Fixed shipping charges, actual shipping costs used with API to pass information to shipping companies. Also handling charges and discounts can be done using this system.

Since there are an infinite number of ways to charge a customer this system does not assume how the store owner can build a charge and what methods that will be used. So this system is complete extensible and new components can be added by a developers to do any additional method that is required. But there are a number of built-in components which can be used by the store owner to build the charge as they need. This should cover most requirements but there is always methods that the system does not know about such as shipping calculation interfaces which will need to be built by developers and released.