Can I add either Read Receipt Request or failing that a copy email to ourselves when an invoice is emailed by you - to give some assurance of its arrival at customer?

Hello commiunityoil,

There is no way to set up a read receipt request, however the status of the invoice within the product will change to viewed once opened (and the customer has selected review and pay). You can set up for all invoices to be copied to yourself by going to the cog wheel > account & settings > sales > messages and filling in the 'Copy (Cc) new invoices to address' box.

Thanks,

Talia