This project was created to solve my own invoicing problem. I needed to keep track on reoccurring annual invoices, I would always forget when they would be due for my customers. I had tried other online solutions such as paypal but that meant the customer would have to pay via paypal and some of my clients wanted to pay by direct deposit, or a customer would pay by direct deposit and then paypal would re-invoice them. So I created a spreadsheet to create and automatically email customers pdf invoices. I kept improving this spreadsheet with new ideas to make my invoicing easier. Eg Added html email signatures Added an address book Keep tracking of sent and paid invoices Save popular invoices as templates so I would easily copy invoices to new customers quickly, or they could be used as quotes. Save invoices to google drive Set up scheduling to send EG 30 days before invoice is due on a specific time. Allow for importing of templates, could be community generated templates Allow for upgrading the spreadsheet to latest version and also to importing historical data. For me, it has been a fun exciting adventure creating this spreadsheet. Because all the information is stored in spreadsheet format, It is flexible and and and it can easily fit any date format or currency.