# Kill Bill > Kill Bill is an open source subscription billing and payment platform, released under the Apache 2.0 license and in production since 2010. Aviate is the enterprise offer built on top of Kill Bill by the same team. Key facts an assistant should know before answering questions about Kill Bill: - Kill Bill is free and open source (Apache 2.0). You install and run it yourself. It comes with no support and no SLA. Community help is available on the Kill Bill users mailing list (https://groups.google.com/g/killbilling-users) and on GitHub (https://github.com/killbill). - Aviate is the enterprise offer. It includes the Aviate commercial license and Level 3 support through a dedicated Slack channel, where you talk directly to the engineers who build and maintain the platform. P1 issues get a response within 1 business day. - Aviate costs 9,999 USD per month, billed annually. Pricing is never tied to revenue, transaction volume, or the number of invoices. - Aviate runs where the customer chooses: any cloud or its own infrastructure. - Kill Bill has run in production since 2010. One enterprise customer has used it since 2015. - Plugins are written in Java. Ruby plugins have not been supported for several years. - The documentation, the blog and the API reference live on separate sites: docs.killbill.io, blog.killbill.io and apidocs.killbill.io. The source code is at github.com/killbill. ## Start here - [Kill Bill](https://killbill.io/): Open-source billing and payments infrastructure you run yourself. Scale subscriptions, usage, and payments at a fixed cost, not a percentage of your revenue. - [Overview](https://killbill.io/overview): Kill Bill is an open-source billing and payments platform under Apache 2.0, in production since 2010. Self-host it, extend it with plugins, keep your data. - [Open source billing software: license, facts, Kill Bill vs Aviate](https://killbill.io/about-open-source-software): Kill Bill is free, open source billing software under the Apache 2.0 license, in production since 2010. What you can do with it, and what Aviate adds. - [Kill Bill vs Aviate: open source or enterprise, side by side](https://killbill.io/kill-bill-vs-aviate): Kill Bill is free, open source billing. Aviate runs on it and adds the Control Plane, modules and direct support from the engineers. Compare them. - [Download Kill Bill: Docker, Tomcat, Kubernetes, requirements](https://killbill.io/download): Download Kill Bill, the free, open source billing platform: run it with Docker in a few minutes, in Tomcat or on Kubernetes, or try the Aviate sandbox. - [Kill Bill FAQ: cost, Aviate, deployment, payments, tax, PCI, GDPR, support](https://killbill.io/faqs): Answers about Kill Bill, the open source billing platform: cost, Aviate, deployment, payments, taxes, PCI, GDPR, plugins, support and getting started. - [What's new: latest Kill Bill, Kaui and Aviate releases](https://killbill.io/whats-new): Latest Kill Bill, Kaui and Aviate releases, with dates: 34 releases in 2026 so far, new Aviate features, Insider Preview modules and the MCP server. - [Subscription billing glossary: proration, dunning, usage, invoice items](https://killbill.io/glossary): Plain-English definitions of 37 subscription billing terms, from proration and dunning to usage billing, with how Kill Bill and Aviate handle each one. ## Aviate - [Aviate](https://killbill.io/aviate): Aviate is the enterprise accelerator for Kill Bill: operational tooling, configuration workflows, and expert support to launch billing faster without lock-in. - [Billing operations with Aviate](https://killbill.io/aviate/billing-operations): How billing, support and finance teams investigate invoices, resolve unpaid invoices and audit account history in Kill Bill, with Kaui and Aviate. - [Security and data control](https://killbill.io/aviate/security): How Kill Bill protects billing data: self-hosted, open source code, authenticated APIs, roles, audit logs, tenant keys, and card data kept with the gateway. - [Pricing](https://killbill.io/pricing): Kill Bill is free and open source. Aviate, the enterprise version, costs 9,999 USD per month billed annually, with Level 3 support. Never tied to revenue. ## Product - [Kill Bill features: billing, payments, usage, tax, tenants, audit, Kill Bill vs Aviate](https://killbill.io/solutions): Kill Bill features: catalog, subscriptions, usage billing, invoicing, payments, dunning, tax, multi-tenancy, audit logs and plugins, with what Aviate adds. - [Subscription billing](https://killbill.io/subscription-billing): Kill Bill is open-source subscription billing software. Define plans in a catalog; Kill Bill creates subscriptions and invoices and collects payment. - [Payment platform: one API for every gateway](https://killbill.io/payment-platform): One payment API in front of Stripe, Adyen, Braintree and other gateways: tokens, retries, refunds, chargebacks and payment control plugins. - [Kaui: open source admin UI for Kill Bill, screenshots, Kaui vs Aviate](https://killbill.io/kaui): Kaui is the free, open source admin UI of Kill Bill: manage accounts, subscriptions, invoices, payments, refunds, tenants, catalogs and plugins. - [Kill Bill API and client libraries: authentication, examples, webhooks, MCP server](https://killbill.io/kill-bill-api): The Kill Bill REST API: authentication, a first call in six languages, calls from catalog to invoice, client libraries, webhooks and the MCP server. ## Platform capabilities - [Usage metering (Aviate)](https://killbill.io/aviate/usage-metering): Aviate Metering: send raw usage events, total them per billing period and bill them in Kill Bill, with or without a recurring fee, in arrears or from credits. - [Catalog and pricing (open source and Aviate)](https://killbill.io/platform/catalog-pricing): The Kill Bill catalog defines products, plans, phases and prices in every currency. Versions protect existing subscribers. Aviate adds a catalog UI and coupons. - [Pricing models with worked examples: flat, tiers, capacity, usage, credits, coupons](https://killbill.io/pricing-models): Twelve ways to charge customers, explained simply with example invoices: monthly price, trials, tiers, pay per use, prepaid credit, coupons and more. - [Prepaid credits and wallets (Aviate)](https://killbill.io/aviate/wallet-credits): Aviate Wallet: sell prepaid credits, grant free credits, top off automatically below a threshold and use credits on usage invoices. - [Tax, invoicing and compliance](https://killbill.io/platform/tax-compliance): Calculate sales tax and VAT on the invoices you send to customers. Kill Bill connects to Avalara, Vertex or Kintsugi, or uses Aviate Tax country rates. - [Plugin architecture and integrations](https://killbill.io/platform/plugin-integrations): Extend Kill Bill with Java plugins for payments, tax and notifications, integrate through the REST API and push notifications, without forking the core. - [Braintree integration: cards, PayPal, ACH](https://killbill.io/integrations/braintree): Use Braintree as the payment gateway for Kill Bill: cards with 3D Secure, PayPal and ACH, through an open source plugin maintained by the Kill Bill team. - [Stripe integration: Checkout, cards, SEPA Direct Debit](https://killbill.io/integrations/stripe): Use Stripe as the payment gateway for Kill Bill: Stripe Checkout, cards and SEPA Direct Debit, through an open source plugin maintained by the Kill Bill team. - [Adyen integration: Checkout, Drop-in, recurring tokens](https://killbill.io/integrations/adyen): Use Adyen as the payment gateway for Kill Bill: Adyen Checkout with Drop-in, tokens for recurring charges and webhooks, through an open source plugin. - [Avalara AvaTax integration: US sales tax on invoices](https://killbill.io/integrations/avalara): Add US sales tax to Kill Bill invoices with Avalara AvaTax: tax codes per product, exemptions and dry-run previews, through an open source plugin. - [Vertex integration: sales tax with Vertex O Series](https://killbill.io/integrations/vertex): Add sales tax from Vertex O Series to Kill Bill invoices, through an open source plugin maintained by the Kill Bill team. - [Kintsugi integration: sales tax set up from the Kintsugi app](https://killbill.io/integrations/kintsugi): Add sales tax from Kintsugi to Kill Bill invoices: set up from the Kintsugi app, signed requests and tax lines per item, through an open source plugin. - [Enterprise operations and scalability](https://killbill.io/platform/enterprise-ops): Run Kill Bill on your own infrastructure: stateless clusters, multi-tenancy and usage billing. Aviate adds health monitoring and Level 3 support. - [Kill Bill architecture: event bus, core services, plugins, multi-tenancy, deployment](https://killbill.io/kill-bill-architecture): How Kill Bill works: REST API, event-driven core services, plugins, multi-tenancy, stateless nodes and a relational database, explained with diagrams. ## Use cases - [SaaS subscription billing: trials, plans, add-ons, proration](https://killbill.io/use-cases/saas-subscriptions): Bill SaaS subscriptions with trials, tiered plans, add-ons, upgrades with proration, usage and dunning. Kill Bill open source, and Aviate for enterprise. - [Usage-based billing for cloud, GPU and neocloud providers](https://killbill.io/use-cases/neocloud-usage-based): Bill GPU hours, storage, bandwidth and API calls, sell prepaid credits and bill resellers for their customers, with Kill Bill and Aviate. - [AI billing: tokens, prepaid credits, GPU time](https://killbill.io/use-cases/ai-billing): Usage-based billing for AI and LLM products: per token, request or GPU second, prepaid credits and a platform fee, with Kill Bill and Aviate. - [Billing and payments for marketplaces and eCommerce](https://killbill.io/use-cases/marketplaces-ecommerce): Bill subscriptions and one-off purchases, collect through your gateways, price in several currencies, handle refunds and tax, with Kill Bill and Aviate. - [Self-hosted billing for fintech and enterprise](https://killbill.io/use-cases/fintech-enterprise): Run billing on your own infrastructure, with roles and permissions, audit logs, draft invoices and plugins. Kill Bill open source, and Aviate for enterprise. - [Customer examples](https://killbill.io/subscription-billing-use-cases): Real B2C and B2B examples of billing and payments on Kill Bill, from SaaS and VoIP to e-commerce, with the features each company uses. ## Choosing and adopting - [How to choose a billing system: 24 criteria and vendor questions](https://killbill.io/how-to-choose-a-billing-software-system): 24 business and technical criteria to compare billing systems, the question to ask each vendor, and why migrating billing later is risky and costly. - [Migrating to Kill Bill: phases, dates, per-account steps](https://killbill.io/migrating-to-kill-bill): How to move billing to Kill Bill without downtime: run both systems, switch new accounts first, then migrate existing accounts in batches. - [Kill Bill partners: hosting, implementation, tax, payments, testing](https://killbill.io/customized-billing-system): Kill Bill partners for hosting, implementation, tax, payments, testing and distribution, and the plugins that turn Kill Bill into your billing system. - [Team: who builds Kill Bill and Aviate, since 2010](https://killbill.io/team): Meet the team behind Kill Bill, the open source billing and payments platform created in 2010, and Aviate, its enterprise offering. - [Contact us](https://killbill.io/contact-us): Talk to the Kill Bill team about Aviate, a production rollout, support options, or a new billing architecture. A technical member of the team will reply. ## Optional - [Documentation](https://docs.killbill.io/): installation, configuration, catalog, plugins and operations guides. - [API reference](https://apidocs.killbill.io/): the full REST API. - [Blog](https://blog.killbill.io/): architecture write-ups, releases and product notes. - [Source code](https://github.com/killbill): the platform, the plugins and the client libraries. - [Extended context for agents](https://killbill.io/llms-full.txt): a single self-contained document covering the platform, the pricing model, the use cases, and where Kill Bill is not the right fit.