Overview

Founded in 2010, Kill Bill provides APIs for pricing models, subscriptions, invoices, and payment gateway integrations. Kaui, its web-based back-office interface, lets staff configure price books and manage subscriptions and payments. This pairing gives technical teams a billing foundation with an administrative interface, rather than a turnkey billing service by default.

Subscriptions and usage-based billing make it relevant to businesses with recurring or variable charges. The open-source core also leaves room to shape billing workflows around a business's needs, but that control matters most to teams equipped to take responsibility for the system.

Key features

Billing operations

Kill Bill supports multi-currency billing, proration controls, dunning automation, and tax automation alongside subscriptions, invoices, and usage-based pricing. Those capabilities cover several recurring-revenue tasks; teams should weigh that breadth against the work of configuring and operating their chosen deployment.

Payment integrations

Plugins connect the payment platform to gateways, issuing banks, and fraud tools. Named integrations include Stripe, Adyen, PayPal, Braintree, GoCardless, and Coinbase, as well as tax services Avalara and Vertex. The plugin approach suits businesses that want to choose their own payment stack, though it is less appealing to buyers seeking a single, ready-made payment workflow.

Security and compliance controls

The platform describes encryption at rest and in transit, TLS communications, AES-256 encryption for stored data, audit logs, role-based access controls, and multi-tenant isolation. Its technical controls are intended to help enterprises meet SOC 2 and PCI-DSS requirements; they are not a substitute for an organisation's own compliance work.

Pricing

Kill Bill uses a freemium model, with paid plans from $40/mo. The options differ substantially in who manages the system, so compare operational responsibility as well as price.

Self-Hosted Open Source: custom pricing. The open-source core runs on infrastructure you control, giving your organisation control of its data and deployment. Community support is included; your team operates and upgrades Kill Bill, while paid support tiers are purchased separately. This is the natural fit for teams able to manage the stack.
Hosted Platform (ChaChing): custom pricing under a separate commercial model. It is fully managed and uses the same Kill Bill APIs and data model, making it the option to consider when you want managed hosting rather than customer-operated infrastructure.
AWS Marketplace: about $40/mo, plus AWS infrastructure costs. Kill Bill runs in your AWS account, but you operate the stack. This is a paid entry point for AWS customers who want to manage their own deployment; the infrastructure bill is additional.

A free plan is available, and a free trial is offered. No trial duration or plan quotas are provided, so there is no basis for comparing a trial period or free-plan cap. The key cost distinction is clear: the Marketplace plan starts around $40/mo before AWS costs, while hosted use follows a separate commercial model.

Platforms

Kill Bill supports API, web, self-hosted, Linux, macOS, and Windows environments. Docker and Tomcat are installation options, and it can run on Windows, Mac, or Linux computers or on a Linux cloud server. That range supports customer-managed deployments across common operating environments, but does not remove the need to operate and upgrade them.

Who it's for

Kill Bill is a strong candidate for online businesses, startups, and growth-stage companies that need customizable subscription, usage, invoice, and payment workflows. It is particularly suited to teams that want to shape billing through APIs and plugins, and have the people or commercial arrangement to manage deployment. Businesses seeking a fully managed service should compare the hosted option; those unwilling to manage a self-hosted stack should not treat the open-source core as a hands-off solution.

Pros and cons

Pro: APIs cover pricing models, subscriptions, invoices, and payment integrations, giving technical teams room to build billing workflows around their requirements.
Pro: Plugin connections include major gateways and tax services, while multi-currency billing, proration, dunning, and tax automation address common recurring-revenue needs.
Pro: The self-hosted open-source option gives customers control over infrastructure and data, with community support included.
Con: Self-hosted customers must operate and upgrade the platform; paid support is separate, so the apparent low-cost route still requires operational capacity.
Con: AWS Marketplace pricing is about $40/mo plus infrastructure costs, and the customer still operates the stack.
Con: Hosted use follows a separate commercial model, so it does not share the Marketplace plan's stated starting price.

Alternatives

For a directory of options in related categories, compare Payment Processing Software, Subscription Billing Software, and Dunning Management Software.

Helcim is a better fit if you want payment processing with no account monthly fees and are comfortable with interchange-plus transaction rates that vary by volume, rather than building around Kill Bill's billing APIs.
Mollie suits businesses seeking pay-as-you-go processing with no contract or commitment and published consumer-card rates, rather than a self-hosted billing platform.
PayPal Invoicing is a simpler choice for creating and sending invoices without setup or subscription fees, with transaction fees when customers pay; Kill Bill is the stronger fit for customizable billing workflows.
Airwallex Payments offers a free Explore plan for online card and local payment acceptance, with processing fees applying; choose it when payment acceptance is the focus rather than configurable subscription billing.
Checkout.com offers tailored pricing based on business profile, and free processing for registered charities in countries where it operates; it is an alternative to consider for payment processing.
Clover POS is a POS-focused alternative with Starter and Standard plans, rather than an API-centered billing platform.
SumUp Invoices offers a free plan with unlimited invoices and quotes, recurring invoices, and customer management; it suits invoice-led needs better than a customizable billing platform.
MobilePay is a free mobile payment option for Android and iOS with a 0.99% transaction fee; consider it for that mobile-payment use case instead.

Verdict

Choose Kill Bill if your business needs programmable subscription and usage billing, broad payment integrations, and control over its billing infrastructure or a managed arrangement built on the same APIs. The main reason to choose it is the combination of extensible billing capabilities and deployment control. Look elsewhere if you need a simple invoicing or payment-acceptance product, or if you cannot take on self-hosting operations and do not want a separate hosted commercial model.

	Kill Bill	SlimPay
Free plan	Yes	No
Free trial	Yes	No
Paid from	Free	—
Open source	No	No
Platforms	api, Linux, macOS, self-hosted, Web, Windows	Android, api, iOS, Web
Free plan	Yes	No
Paid from	40 /mo	—
Multi-currency support	Yes	—

Kill Bill vs SlimPay

Kill Bill

SlimPay