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.
InvoicePlane is a self-hosted open source application for managing your quotes, invoices, clients and payments. The application comes with various options, templates and settings to customize your invoicing experience.
From invoicing to expense tracking to accounting, Akaunting has all the tools you need to manage your money online, for free.
Manager is free accounting software for Windows, Mac and Linux.
It features an intuitive and innovative user interface with modules such as cashbook, invoicing, receivables, payables, taxes and comprehensive financial reports.
The desktop edition is free while the cloud edition.
Zoho Books is a simple, easy-to-use accounting app that tracks the money coming in and going out of your business. With Zoho Books, you can always stay up-to-date on your business finance and make decisions instantly.
Send, track and collect payments quickly. Great for teams, freelancers and service providers. FreshBooks is an easy cloud accounting app for small businesses and freelancers, specifically designed to save you time billing clients.