Kill Bill

Kill Bill is an open source billing platform designed for subscription-based businesses. It handles recurring billing, invoicing, payment collection, and account management. The system is built around a plugin architecture that lets you customize everything from payment gateways to notification channels. It supports complex pricing models including tiered, volume-based, and per-unit pricing.

The platform integrates with over a dozen payment gateways including Stripe, PayPal, Adyen, and Braintree. It offers a RESTful API, webhook support, and real-time analytics through its admin UI. Kill Bill runs on Java and uses MySQL or PostgreSQL for storage. The project was created by the team behind the commercial billing service Kill Bill Cloud and has been in active development since 2013.

Kill Bill is ideal for SaaS companies, IoT services, and any business that needs flexible recurring billing without vendor lock-in. It is released under the Apache 2.0 license, meaning it is free to use and modify. The community edition is fully functional, while Kill Bill Cloud offers hosted and enterprise support options for organizations that want a managed experience.