The business utilities on most sites are lead magnets: free until the useful part, then an account, then a subscription. These are not. The invoice prints straight to PDF through your browser, and the QR codes encode your data directly rather than pointing at a redirect service that can change its pricing or shut down.
That second point matters more than it sounds. A QR code on a printed poster or a business card outlives the company that generated it, unless the code was a short link to that company’s server.
Questions
Do the QR codes expire?
No. The data is in the pattern itself, not on a server, so there is nothing that can be switched off.
Can I use the invoice for real invoicing?
Yes, it is free to use commercially. Making sure the content is correct for your jurisdiction remains your responsibility.
Is my data stored?
Only in this browser, so a form is prefilled next time. There is no account and no server copy.