Billing is the capacity to let the system asks (money of course) for its use. This application requires LCR for FusionPBX because when you build a business, you are not only looking to make profits but to save money.
Billing for FusionPBX will allow you get money. Currently, Stripe, Paypal and Off-line plugins are available, but others gateways can be coded. It supports multicurrency as well, you can bill one customer in EUR, other in USD, other in MXN and pay in USD.
The big advantage of this project is it is inside the FusionPBX itself. This allows billing for many other items, such as extra extensions, assigned DID and more.