Most ecommerce hosting plans offer free scripts for shopping carts and even full CRM systems, but many do not provide customers with good invoicing and billing systems. If your business does any type of work that requires invoicing, the following free and open source invoicing systems are choices you might want to consider.
Simple Invoices is PHP-based and features support for recurring payments, sales reports, multiple customers/users, PDF invoices and a variety of payment types. You can install it yourself or use of the service providers supported by the developers.
Still in beta, this invoice creation and management application promises to be basic and secure. It supports recurring invoices, multiple clients, taxes and a tagging system.
Open Source Billing promotes its support of online payment processors such as PayPal so that you can receive online payments. It also features a rather attractive interface with a dashboard of year-to-date income, amount billed and outstanding invoices. You can also export invoices to PDF.
Unlike the others on the list, Ofuz is more than just an invoicing app. It provides many of the features you would expect from a pricey CRM application. You can keep track of clients, collaborate on projects, organize leads, create targeted e-mail forms, track your work time and of course manage invoices. The developers offer both an open source version you can install and a paid online service.
Also PHP based, Fusion Invoice supports online payments from services like PayPal and also features a helpful dashboard similar to Open Source Billing. You can filter through pages of invoices, create guest accounts for clients, import invoice and client data from other systems and create recurring invoices. It is free and open source but also very easy to install.