Simple Invoices & Estimates is described as 'A simple, easy to use Invoices & Estimates program for Windows® Computers. It supports unlimited companies, adding on the fly items, customer list, items list, and easy to understand invoices report. Great for everyday businesses' and is an app in the Business & Commerce category. There are more than 100 alternatives to Simple Invoices & Estimates for a variety of platforms, including Online / Web-based, Windows, Mac, iPhone and Linux. The best alternative is GnuCash, which is both free and Open Source. Other great apps like Simple Invoices & Estimates are ERPNext (Free, Open Source), Odoo (Freemium, Open Source), HomeBank (Free, Open Source) and Wave (Free).
Logic Invoice is an accounting & invoicing solution, which you can use to build websites and online applications. Best of all, Logic Invoice is an open source project, allowing everyone to freely access the source codes and make their own customisations.
Invoice Station helps small business owners around the world invoice their clients. Other major features include: expenses, payments, clients/projects, and analytics. It's fully customizable so it can fit any region or country anywhere on Earth.
Billings is being merged with Billings Pro. Billings Pro is an award winning invoicing and time tracking solution. Built for small businesses, freelancers and working professionals to help their business grow.