Invoice Ninja - Invoice Ninja is a free, open-source solution for invoicing and billing customers.
Square - Square helps millions of sellers run their business-from secure credit card processing to point of sale solutions. Get paid faster with Square. Sign up today!
Harvest - Simple time tracking, fast online invoicing, and powerful reporting software. Simplify employee timesheets and billing. Get started for free.
Lightspeed - retail and restaurant point-of-sale, ecommerce, and omnichannel solution
GnuCash - A personal and small-business financial-accounting software, licensed under GNU/GPL and available for Linux, Windows, Mac OS X, BSD, and Solaris.
Heartland Retail - Heartland Retail (previously Springboard Retail) POS software a robust, user-friendly cloud point of sale solution designed for the business of retail. A complete retail management platform built for growing single, multi and franchise brands.