I can provide additional information with turning off email notifications, @meg16.

You can opt-out those payment notifications by removing the option to send you a copy email message sent with sales forms from the Sales menu. 

Let me show you how:

1. Go to the Gear icon ⚙️ and proceed to the Account and Settings. 
2. Click on Sales and choose Messages. 
3. Remove the check from the Email me a copy at [email address]. 
4. Select Save and then Done.                                         

You can check this article for more information: Email a sales form or report to multiple email addresses.

There's also an option in QuickBooks Online that lets you update the email address that appears on your sales forms, you can refer to this article for detailed guidance: Change the email address your customers see in QuickBooks Online.

Keep in touch if you still have questions in removing the payment notifications. I'm always glad to help in any way I can. Have a wonderful day!