Open-Source Software

Open Source Billing, in Production Since 2010

Kill Bill is free billing and payments software under the Apache 2.0 license. Large companies and startups have run it in production since 2010, and deployments on the platform have invoiced billions of dollars since then.

Kill Bill: open source, Apache 2.0, freeAviate: enterprise features and Premium support

Last updated: November 2026

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Short answer

Is there free, open source billing software?

Yes. Kill Bill is open source billing and payments software under the Apache 2.0 license. You can download it, run it on your own infrastructure, change the code and use it commercially, with no license fee and no fee per transaction. It covers subscriptions, usage, invoices, payments through gateway plugins, retries and multi-tenancy, and it has run in production since 2010. Kill Bill open source comes without support or SLA. Aviate, the enterprise offering built on Kill Bill, adds enterprise features and Premium support for a fixed annual fee, never a share of revenue.

At a Glance

Kill Bill Open Source in Facts

License: Apache 2.0
In production since: 2010
Source code: github.com/killbill/killbill
Cost: Free, with no fee per transaction
Language: Java, with plugins in Java
Java
Databases: MySQL, MariaDB or PostgreSQL
MySQLMariaDBPostgreSQL
Deployment: Docker, Kubernetes or Tomcat, on your infrastructure
DockerKubernetesTomcat
Admin UI: Kaui, also open source
Support: Community help, no support or SLA. Premium support with Aviate
Enterprise offering: Aviate, a fixed annual fee, never a share of revenue

Kill Bill and Aviate

What Is Free, and What Aviate Adds

Aviate runs on top of Kill Bill. Everything in the Kill Bill column stays free.

	Kill Bill open source	Aviate
Billing	Catalog, subscriptions, usage, invoices, credits	Adds a catalog UI, Aviate Coupons, Aviate Wallet, Aviate Metering
Payments	Payment API, gateway plugins, retries, refunds, chargebacks	Adds payment settings in the Aviate interface
Tax	Tax plugins such as AvaTax, Vertex or Kintsugi	Adds Aviate Tax: rates per country and per product
Operations	Kaui admin UI, REST API, multi-tenancy	Adds the Aviate interface and Aviate Health
Support	Community help, no support or SLA	Premium support from the engineers. First response within 1 business day for P1 critical production issues, subject to the applicable support agreement.
Cost	Free	A fixed annual fee, never a share of revenue. Pricing

Try It

Run Kill Bill on Your Laptop

The official Docker images start Kill Bill, Kaui and a database in a few minutes.

Install Docker and Docker ComposeAllow at least 4 GiB of memory for Docker.
Create a docker-compose.yml fileThree services: Kill Bill, Kaui and MariaDB. The getting started guide gives the file.
Run docker compose upAfter a couple of minutes, the Kill Bill API answers on port 8080 and Kaui on port 9090.
Create a tenant, a catalog and an accountThen subscribe the account to a plan and see the first invoice. Getting started guide

Kaui, the open source Kill Bill admin UI, showing a demo customer account with its balance, bill cycle day and next invoice date — Kaui, the open source admin UI of Kill Bill

How to Decide

Open Source or Hosted SaaS Billing?

Both models work. The right one depends on your volumes, your team and how much control you need.

	Self-hosted open source	Hosted SaaS billing
Who runs it	Your team, on your infrastructure	The vendor
Where data lives	In your database, in the region you choose	In the vendor's systems
Cost model	No license fee. You pay for hosting and your team's time	Often a share of revenue or a fee per invoice, so the bill grows with sales
Source code	Public. You can read, audit and change it	Closed
Custom logic	Plugins and code changes	Limited to what the vendor exposes
Upgrades	When you choose	When the vendor ships
Time to start	Longer: you install, integrate and operate it	Shorter: sign up and configure

Illustration, not a quote: no vendor prices on this chart. Kill Bill is free, and Aviate is a fixed annual fee.

Open source billing fits when

Billing volume is high, and a share of revenue would cost too much
Billing data must stay on your infrastructure
Your pricing or payment flows need custom logic
You have engineers who can run a Java service

It is not the right fit when

You have no engineering team to deploy and operate it
You want a hosted tool that works the same day
Your pricing is simple and your volumes are low

Benefits

Why Choose Open Source for Billing?

Billing is the heart of the business. Open source keeps it in your hands.

No license fee

Kill Bill has no license fee or fee per transaction. You pay for the infrastructure, engineering time, support and services you choose.

Illustration: flexible pricing and billing models

Flexibility

Test new pricing and billing models when you need to. The Apache 2.0 core has no usage limits or data query restrictions; support and operating arrangements may have separate terms.

Illustration: a long-term, stable billing system

Stability

The software does not depend on one vendor's future. The code stays public, and the community can maintain it.

Control

Upgrade on your own timeline. Read every line of code, and validate configuration and code changes before production.

Illustration: an open, extensible architecture

Open Architecture

Add your own logic through plugins. Connect your systems and the payment and tax vendors you choose.

Community

Users around the world share solutions on the mailing list and on GitHub. Someone may have solved your problem already.

Open Source, Explained

Common Questions About Free Software

Illustration: open source billing software is free to use

Why does it matter that Kill Bill is open source?

Anyone can download, study, change, run and share the code. Kill Bill is free to use: no monthly charge, no yearly charge, no fee per transaction.

Illustration: businesses using open source software

What businesses use free software?

Startups and global enterprises alike. Open source has existed for decades: WordPress and LibreOffice are open source. See the Kill Bill use cases.

Illustration: Kill Bill installed on your own server or cloud

What can you do with Kill Bill?

Install it on a computer, server or cloud, and bill customers or take payments.
Change the code or add plugins for your sector and processes.
As a consultant, adapt it for your clients.

You do not have to share your changes, although contributions are welcome.

Are there any rules?

Yes, the Apache License 2.0, one of the more permissive open source licenses. You can use Kill Bill commercially. You keep the copyright and license notices when you distribute it, and each contributor grants a patent license for their contributions.

Illustration: auditing open source code for security

Is free software untested or insecure?

The longer software runs, the more engineers read, test and fix it. Because the code is public, your own team can audit it for security reviews and financial controls. Kill Bill security advisories are posted on the community mailing list.

Is free software unsupported?

The community helps on the mailing list, without any SLA. For production support, Aviate includes Premium support from the engineers who build the platform, on a dedicated Slack channel. How support works

To learn more about open source, read the Open Source Initiative and Wikipedia.

In Production Since 2010

Not a Starter Kit. A Production System.

Kill Bill's core has run in production since 2010. It covers the edge cases of real billing: proration, credits, retries, multi-currency and multi-tenancy.

Payment tokenization

With a gateway tokenization flow, Kill Bill stores the token returned by the gateway rather than the card number. Your PCI DSS scope depends on the full payment flow and every system that receives or transmits cardholder data.

Multi-Tenant White-Label

One deployment can run many tenants, each with its own catalog, accounts and payment configuration.

Complex Billing Models

Usage-based billing (AI tokens, API calls), recurring fees, billing in advance or in arrears, proration and credits.

Your Payment Gateways

Open source plugins for Stripe, Adyen, Braintree and Hyperswitch, or your own plugin. Payment platform

Stripe

BraintreeHyperswitch

Your Tax Engines

Open source tax plugins for Avalara AvaTax, Vertex and Kintsugi compute tax on each invoice. Aviate Tax adds rates per country and per product. Tax compliance

Kintsugi

Open source vs Aviate: what is free, what is paid Kill Bill is the open-source billing engine. Aviate is its enterprise edition: the same engine, with product, pricing, commercial workflow, usage, billing and revenue capabilities and Premium support. Download Kill Bill: Free, Open Source Billing Software 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. What's New in Kill Bill and Aviate, 2026 Latest Kill Bill, Kaui and Aviate releases, with dates: 34 releases in 2026 so far, new Aviate features, enterprise modules and the MCP server. Kill Bill Overview: Open-Source Billing and Payments 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.

FAQs

Open Source Billing FAQ

Is Kill Bill really free?

Yes. Kill Bill is open source under the Apache 2.0 license. There is no license fee and no fee per transaction. You host and run it yourself, and Kill Bill open source comes without support or SLA.

What license does Kill Bill use?

Kill Bill uses the Apache License, Version 2.0. You can use, change and distribute the software, including commercially. You keep the copyright and license notices, and each contributor grants a patent license for their contributions.

Do I have to publish my changes to Kill Bill?

No. The Apache 2.0 license does not require you to share your changes or your plugins, although contributions back to the project are welcome.

Can a consulting company use Kill Bill for its clients?

Yes. Consultants and integrators can install, change and extend Kill Bill for their clients under the Apache 2.0 license.

Is open source billing software secure?

The code is public, so your team can audit it. Kill Bill runs on your own infrastructure, card data is tokenized by the payment gateway, and security advisories are posted on the community mailing list.

Who supports Kill Bill?

The community helps on the mailing list, without any SLA. Aviate, the commercial enterprise revenue platform built on Kill Bill, has Premium support from the engineers who build the platform on a dedicated Slack channel. First response within 1 business day for P1 critical production issues, subject to the applicable support agreement.

What is the difference between Kill Bill and Aviate?

Kill Bill is the open source billing and payments platform. Aviate runs on top of it and adds enterprise features, such as a catalog UI, coupons, prepaid credits, metering, country tax rates and health monitoring, plus Premium support, for a fixed annual fee.

How long has Kill Bill been in production?

Since 2010. Deployments on the platform have invoiced billions of dollars since then.

How do I try Kill Bill?

Install Docker and Docker Compose, create a docker-compose.yml file with Kill Bill, Kaui and MariaDB, and run docker compose up. After a couple of minutes, the API answers on port 8080 and Kaui on port 9090. The getting started guide on docs.killbill.io gives the file and the next steps.

When is open source billing software not the right choice?

When you have no engineering team to deploy and operate it, when you need a hosted tool that works the same day, or when your pricing is simple and your volumes are low. A hosted SaaS billing tool is then often simpler. Open source billing fits better at high volumes, when data must stay on your infrastructure, or when pricing needs custom logic.