Open source Invoice software

jBilling

jBilling is a web-based enterprise billing and rating system. It manages your subscribers with automatic invoicing (email and PDF) and payment processing (credit cards, checks, direct deposit). Robust, well documented and easy to use! (GPL)

Cross-platform

Siwapp

Siwapp is an open source web application meant to help manage and create invoices in a simple, straightforward way. (MIT)

Cross-platform

2 applications