WHMCS - WHMCS is an all-in-one client management, billing & support system for online businesses.
Atomia Billing Platform - An enterprise billing system for hosting providers. You can run Atomia on your own infrastructure.
HostBill - HostBill is a powerful and flexible, all-in-one automation, billing, client management and support platform for online businesses.
Hosting Controller v10 - Hosting Controller is a Hybrid automation solution for On-premises and Cloud service providers.
Blesta - Blesta is professional client management, billing, and support software.
sourceDESK - sourceDESK is a complete solution for web hosting and online businesses providing automation for all important business processes. This includes product creation, payments, support and accounting.