About these invoicing tools
The invoice generator works entirely in your browser: the names, addresses and amounts you type are not sent to a server, and they are gone when you close or refresh the page. There is no account to create.
An invoice is a practical business document, and the rules for what it must contain differ by country and by whether you are registered for VAT, GST or sales tax. The tool gives you a clean layout and correct arithmetic; it does not check that your invoice meets the rules where you work. Ask your accountant or your tax authority what yours must show.