Invoicer is an Invoicing application designed and built by Thomas Sankara, whose main purpose is to - as the name suggests - create and send invoices to clients, because this is something I've struggled with before. I hope it helps you as well.
Please note that even though most of the functionality is done, there are still some things to add such as saving invoices, and improving the login and Logout experience. Thank you as you bear with me.