Bill Items are essential to Invoicing. You must create them before creating your first contract. Each Service Model in your contract must be linked to at least one Bill Item. Bill Items will also be displayed on each invoice when the specific service has been provided. You will be able to look at billing analytics per Bill Items.
To set up your Bill items, follow the path below:
Settings > Bill Items > New Bill Item
You can decide how you need your Bill items to be created as they can be particular to the type of service offered or more generic.