What it does
Kill Bill is an open-source subscription billing platform with a browser administration app called Kaui. Businesses configure catalogs, customer accounts, subscriptions and invoices, then connect payment or tax services through plugins. The Apache-2.0 core is free to operate on your own infrastructure; Aviate adds paid commercial modules and support.
Kill Bill suits teams that want to operate the billing engine themselves. Its core handles subscriptions and invoices, while plugins connect services such as payment gateways and tax calculation. Kaui provides a browser interface for administration.
Installation brings together Kill Bill, Kaui and a database. The local setup supports Windows, Mac and Linux, and the container setup runs these components together. This is software your team deploys and maintains.
In Kaui, sign in and create a tenant, which separates a business's data and configuration. Add its product catalog, create a customer account and assign a subscription plan. The account's Invoices section then lets you open the generated invoice. A real payment-gateway connection is a separate part of collection.
The quick-start catalog editor is useful for learning, but it supports only a subset of the full catalog format and is explicitly unsuitable for production. Production pricing needs the full catalog configuration. That distinction matters for teams expecting to manage every price rule through a simple form.
Free core and Aviate
The open-source core has no Kill Bill license charge. Your costs include infrastructure, operations and any connected service. Community support has no service-level commitment.
Aviate is listed at USD 9,999 per month, billed annually. It runs in your cloud or on your infrastructure and adds commercial modules such as raw-usage metering, wallets, coupons and additional invoicing controls. Its Level 3 support includes a stated one-business-day first response for critical P1 incidents, not a one-day resolution promise.
Core usage reporting and account credits are different from Aviate's metering and wallet modules. Likewise, core tax plugins should not be confused with Aviate's supplied tax-rate features. Compare the specific module needed before assuming a free deployment includes it.
Kill Bill is a practical fit for an engineering-led billing operation with responsibility for hosting and integrations. It asks more of that team than a hosted invoice editor, but exposes the catalog, tenant and payment connections for direct control.
Strengths
- Separate tenants keep billing data and configuration distinct.
- Plugins allow payment and tax services to be connected to the core engine.
- The free core includes subscription and invoice handling without a platform transaction charge.
Watch out for
- Your team must operate the application, database and upgrades.
- The quick-start catalog editor is not suitable for production.
- Advanced Aviate modules and direct engineering support require a commercial subscription.
Best for
- Engineering teams operating their own subscription billing
- Businesses needing separate tenant billing configurations
- Organizations connecting custom payment and tax services
Sources
- Kill Bill free core and Aviate pricing comparison (Oct 27, 2026)
- Official Kill Bill repository and Apache 2.0 license (Oct 27, 2026)
- Install Kill Bill, Kaui and the billing database (Oct 27, 2026)
- Kaui tenant, catalog, account and subscription quick start (Oct 27, 2026)