Simple Invoices is described as 'Free, open source, web based invoicing system that you can install on your server/pc or have hosted by one of our services providers' and is a Invoicing software in the business & commerce category. There are more than 100 alternatives to Simple Invoices for a variety of platforms, including Web-based, Windows, iPhone, Mac and iPad apps. The best Simple Invoices alternative is Paymo, which is free. Other great apps like Simple Invoices are Wave, WorkTime, SmoothLedger and TimeCamp.