1.Open the invoice from Invoices.
2.Press Send by email. The customer's address is filled in from their record — you can type others, separated by commas.
3.The subject and message are pre-written and editable. Whatever you type here appears above the invoice in the email.
4.If the invoice has files attached, each one appears with a checkbox. Nothing is attached unless you tick it.
5.Press Send.
The invoice itself always goes as a PDF, and the same document is shown in the body of the email so it can be read without opening an attachment.
Why an attachment is not ticked by default
An invoice often carries things the customer should not receive — a supplier quote showing your margin, an internal photo. A checkbox that started on is how one of those leaves the building.