There are 2 types of invoice items - Regular invoice item and Smart invoice item.
Regular invoice items
Regular invoice items are also used for one-time fees such as:
Registration fee
Material fee
Deposit
Here is an example of a Regular Invoice item for Registration fee:
Smart invoice items
Smart invoice items are used when a variable amount is charged for each time period (such as a month or a term). It is named "Smart" billing as the system is able to count the number of lessons in the time period and bill accordingly by using the per lesson fee multiplied by the number of lessons counted.
Here is an example of a Smart invoice item for 1 lesson:
