Stripe Terminal - The programmable point-of-sale solution 💳🛠️
Invoice Ninja - Invoice Ninja is a free, open-source solution for invoicing and billing customers.
Square Register - A fully integrated point of sale (POS) system 💰
Harvest - Simple time tracking, fast online invoicing, and powerful reporting software. Simplify employee timesheets and billing. Get started for free.
RoyalPOS - Point of sale system for restaurants & retail stores
GnuCash - A personal and small-business financial-accounting software, licensed under GNU/GPL and available for Linux, Windows, Mac OS X, BSD, and Solaris.