Kill Bill - Open-Source Subscription Billing & Payment Platform

Kill Bill is the open-source subscription billing and payments platform. It supports Subscription engine, with plans management (trial, upgrade, downgrade, etc.), support of add-ons, bundles with multiple subscriptions, Invoicing engine, supporting different billing alignments, recurring and one-time charges, international tax, metered billing, Payment state machine, with payment routing capabilities, supporting dozen of gateways and lot more.