Invoice Ninja

Invoice Ninja is a free, open-source solution for invoicing and billing customers. With Invoice Ninja, you can easily build and send beautiful invoices from any device that has access to the web. Your clients can print your invoices, download them as pdf files, and even pay you online from within the system. Invoice Ninja is managed by a team of seasoned web workers. We launched in early 2014 and have been thrilled by the enthusiastic response we’ve received from our growing community of users.

Screenshots from Chrome Web Store