WHMCS - WHMCS is an all-in-one client management, billing & support system for online businesses.
Chargebee - Chargebee lets you manage subscriptions and payments at scale, handle custom recurring billing scenarios, reduce subscription churn and simplify accounting.
Atomia Billing Platform - An enterprise billing system for hosting providers. You can run Atomia on your own infrastructure.
Recurly - Subscription billing and recurring billing management. Recurly offers enterprise-class subscription billing for thousands of companies worldwide.
Hosting Controller v10 - Hosting Controller is a Hybrid automation solution for On-premises and Cloud service providers.
Zuora - Zuora creates cloud-based software on a subscription basis that enables any company in any industry to successfully launch, manage, and transform into a subscription business.