Originally Posted by Germanius
It depends on what you want to have.
As far as I know the ISPC billing module is just a simple solution for invoicing some services.
But “WHMCS is an all-in-one client management, billing & support solution for online businesses. Handling everything from signup to termination, WHMCS is a powerful business automation tool that puts you firmly in control”.
So you have to choose: ISPC billing module or WHMCS and ISPC Server Module.
It depends on what you need and if you want to be able to offer all functions form ispconfig to your cutomers or if the functions availbly trough whmcs are enough for your needs. The ISPConfig billing module offers more then just creating invoices as Germanius told, it offers direct billing and intgrates the invoices in the ISPConfig dashboard etc., the support system is available in ispconfig as well. The benfit of the Billing module is its tight integration in ISPConfig and it can also be connected directly to your hosting website plus you dont have to provide different Logins for billing and server management to your customers. So while whmcs + ispconfig is just a loosely coupled system, the billing module offers a integrated system were all ISPConfig funtions are available plus a single sign on for your customers.