Thank you for reaching out to us here in the Community, Andrea.
It appears that you've posted a duplicate post regarding sending invoice. My colleague, @EduardA, has provided a recommended solution. I encourage you to review the suggested response, which you can find here: https://quickbooks.intuit.com/learn-support/en-uk/other-questions/re-when-i-have-created-my-invoice-....
Please feel free to come back and visit us here in the Community if you have any further questions about sending invoices. We're always here to help and will ensure to respond to your inquiries as quickly as possible.