Invoice Ninja is described as 'Free, open-source invoicing tool with PDF generation, online payment support, invoice templates, multi-gateway integration, and business customization options' and is a Time Tracking tool in the business & commerce category. There are more than 100 alternatives to Invoice Ninja for a variety of platforms, including Web-based, iPhone, Mac, Windows and Android apps. The best Invoice Ninja alternative is Midday. It's not free, so if you're looking for a free alternative, you could try Summit Finance or Cattr. Other great apps like Invoice Ninja are Clockify, InvoicePlane, Akaunting and Manager.