Thanks for chiming in on this thread, Demux Dave.

In QuickBooks Online, we have the Customer-facing email option. The email address entered in this field is one that your customer will see when they view the invoice.

Here's how you can edit the email address:

1. Click the Gear > Account and settings.
2. On the left panel, click Company.
3. In the Contact info section, edit the email address in the Customer-facing email field.
4. Hit Save and then Done. 

You can also see this sample screenshot for reference:

If you need to customize your sales forms, feel free to read this article: Customize invoices, estimates, and sales receipts in QuickBooks Online.

Please, let me know if there's anything else you need. Me and my colleagues are always here to help. Take care!