The quickbooks self employed system is a bit hit and miss with invoices. I have had clients complaining they've not recieved them at all, even after having checked spam. Others have complained that all of the information is not there and they can't pay me. Of course you can't check what's been sent via a sent items box either. I've now given up, and prefer to send a PDF, doing this is quite complicated because you can't save as a PDF untill you sent it. The work around is to send it to your own email address, and then save as a PDF from the system. Just appolgise to the client that the email address is not right. This is the only way to do it and keep the invoice on the system. Saving it as a draft and then PDF means it stays for ever as a draft untill you send it to someone.