Hello, ramprentacar.  

Thank you for reaching out to us. If the bank details are on the template, you can update the template, but if the bank details are on the body of the email, update the Message content in the Sales settings.

Here's how:

1. Click the Gear icon and choose Account and Settings.
2. Select Sales, modify the info under Messages.
3. Tap Save and Done.

I've added this article for more information about invoicing: Customize invoices, estimates, and sales receipts in QuickBooks Online. 

If you have other questions about your accounts in QuickBooks, please don't hesitate to visit the Community again. I'm here to help. Take care!