Kill Bill
killbill · Payments
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What is Kill Bill?
Kill Bill supplies the accounting machinery behind subscription products rather than a fixed storefront. Product catalogs describe plans and phases; account timelines capture subscriptions and changes; invoicing, payment attempts, retries, credits, and events then provide a programmable foundation for a business-specific billing system.
Kill Bill is an open-source platform for subscription billing and payments. Its modular design lets teams integrate, replace, or disable components while retaining control of business and client data.
Core capabilities
- Model plans, phases, add-ons, usage, pricing, and effective catalog versions
- Generate invoices and orchestrate payments, retries, refunds, credits, and dunning
- Integrate billing through REST APIs, events, plugins, and tenant-level configuration
Billing as an event timeline
Kill Bill records subscription, catalog, invoice, entitlement, and payment changes on account timelines. Effective-dated catalogs and policy controls let the engine determine when a change applies, how a charge is prorated, and which invoice or entitlement events follow.
- subscriptions
- usage
- proration
- invoicing
Composable billing infrastructure
REST APIs and a persistent event bus make the billing core available to external product, customer, and accounting services. Payment and business plugins add gateways or custom behavior, while tenant configuration supports logically separate billing operations on shared infrastructure. Payment gateways and optional commercial services remain separate integrations, not an included storefront.
- REST API
- event bus
- plugins
- multi-tenant
Where it fits
Use cases
- 01
Launch a subscription product catalog
Define products, plans, trial or evergreen phases, recurring and usage charges, add-ons, and price versions, then create account subscriptions against that catalog through the API.
- 02
Handle changes during a billing cycle
Schedule upgrades, downgrades, cancellations, pauses, or add-on changes and let configured alignment and proration policies determine how those events affect entitlement and invoices.
- 03
Build a resilient payment operation
Route invoice balances through payment plugins, react to failures with retry and dunning policies, issue credits or refunds, and consume platform events in surrounding customer or finance systems.