Kill Bill Overview

Open-Source Subscription Billing & Payments Platform
Kill Bill is an open-source billing and payment platform that powers the heart of your business – its revenue.


Visit our YouTube channel for a video introduction to Kill Bill (and more)!

About Our Open-Source Software

Kill Bill uses the Apache Version 2.0 license, one of several licenses approved by the Open Source Initiative.

This means you can freely use, copy, modify, and share Kill Bill.
(Yes, “freely” really does mean that Kill Bill is free!)

To learn more about open-source software, see our OSS Learning page.


We refer to Kill Bill as a platform because of its extensibility. Kill Bill is comprised of…

A standalone Java server

Kill Bill runs on your back-end. Customers don’t interact with Kill Bill directly. Instead, their activities on your website (like purchasing a year’s subscription to your services) triggers API calls to process orders, subscriptions, renewals, and other customer activities. You design and build the API calls that communicate with the Kill Bill platform. 

A relational database

The database manages all the states associated with the subscriptions, invoices, payments, and so forth.

An online user interface

Kaui is an online user interface that lets your back-office people (for example, Finance or Support) interact with Kill Bill. Kaui makes it possible for your employees to manage tasks like issuing refunds and adjusting invoices.

You can deploy and manage Kill Bill and Kaui in your own data center or in the public cloud.

All the basic features to run a billing and payments platform

Kill Bill includes all of the basic features a business needs to run subscription billing processes and payment processes. Thousands of organizations use Kill Bill as their basic billing system with payment processing features.

Modify Kill Bill to exactly suit your business needs

However, the real power of Kill Bill lies in building your own business logic on top of it to create a customized billing and payments solution. You can write plugins to modify Kill Bill’s behavior or integrate with third-party vendors.

Use open-source plugins or create your own 

Kill Bill already has many open-source plugins. You can use them as examples for creating your own or modify them for your own use. For example:

  • Fraud detection solutions (like Accertify or Feedzai)
  • Tax provider solutions (like Avalara AvaTax)
  • Credit card account updaters (like Visa Account Updater)

Who should use Kill Bill?


Honestly, here at Kill Bill, we believe that any business that bills its customers and/or accepts payment online can (and should) use Kill Bill as its billing system.

Maybe you’re frustrated with the lack of customization available from the more popular SaaS billing-payment providers. Or perhaps you’re a startup with a tight budget.

Kill Bill is eminently suitable because it’s affordable, extensible, and – most importantly – secure and stable.

Is Kill Bill right for your business?

We’ve put together a checklist to help you decide if Kill Bill is right for your business: 


Does your business require integration with lesser-known payment gateway providers, such as those used internationally?


Does your business need to use a different fraud detection provider (or account updater or tax provider) than the one used by your payment gateway?


Do you need to run custom, decision-making code? (Examples: change amounts dynamically, abort payments with a rules engine due to fraud detection, modify invoices on-the-fly, customer payment retry logic)


Do you need real-time access to your organization’s data to build analytical and financial reports?


Do you need to integrate with your own internal applications? (Examples: for tax rates or tight integration with your catalog system)
You guessed it… if you answered “yes” to any of these questions, check out Kill Bill’s open-source billing and payments platform features (not to mention Kaui). You can also read over some typical and not-so-typical Kill Bill use cases.