Thanks for coming back, @oneinchpunch. 

In QuickBooks Self-Employed version, you can only enter multiple email addresses to the “BCC” field when creating an invoice. This will send separate emails of the invoice to the email addresses you've entered, rather than creating an email thread. 

Here's how: 

1. Go to the Invoices page.
2. Select Create new Invoice.
3. Enter the email address, then fill the BCC field with any other email addresses you’d like to send a copy of the Invoice to.

However, if you're getting the same result, I recommend contacting our Customer Care Support so we can investigate further.

Here's how to reach out:

1. In your account, go to Assistant at the top right.
2. Scroll down and enter your question in the field. QB Assistant will provide a link to some answers.
3. Type "I still need a human."
4. Choose either Message an agent or Get a callback.

You can refer to this article for additional knowledge: Send an invoice in QuickBooks Self-Employed. It also includes steps on sending an invoice using the mobile apps. 

Feel free to message again if you have additional concerns with anything else. We're always around to help you some more. Take care!