BoxBilling is a web-based, open-source billing and client management application. It is designed to help businesses and freelancers manage their clients and invoices, while also providing an easy way to accept payments. The app offers a range of features, including automated billing, invoicing, credit card processing and payment gateways, client management, support ticket system, and more. It also offers integration with popular payment gateways, such as PayPal and Stripe, as well as with popular web-based services such as Dropbox and Google Drive. BoxBilling is a powerful, yet easy to use tool for any business to manage invoices, customers, and payments.
BILLmanager
WHMCS
HostBill
TheHostingTool
ClientExec
ZBillingNET
WeFact Hosting
BillingServ
Discontinued Has not been updated in years. See https://thehostingtool.com/forum/thread-2283.html