The issue here isn't to see the Invoice, as that is easy, the issue is to see the message sent to the customer in the email page.  Once you change the standard, built in message sent to the customer - the one they read first, before they click on the invoice,  QBO does not keep that message stored, so when you create a new invoice for the same customer and are in the 'send email' form, the Body of the email does not retain your changes, it reverts back to the standard QBO email body text without the changes from the last sent invoice.

Since you can't pull up or see what QBO sent the customer (if you missed clicking on the bcc box, which has to be checked and entered every single time or before you learn about this), you have to re-type the wording from memory, (if you didn't already get burned by this and have every single change for each client in a word doc). 

You can't be sure what the client actually sees in their email from you, if you miss the bcc.  How is that an Audit trail and usable for client disputes? 

Why can't we just see what the customer received, instead of looking through our inboxes for an email bcc'd to us from our QBO.  What if this is one of hundreds of invoices?  Why are we suppose to search through our history of emails to find the one bcc we need?  This doesn't make sense and goes against all the Audit tracking functionality.