Good question! The easiest way to do this is to create an email template in Settings > Email Templates using the merge fields that contain the charges and billing activity. You can then go to the booking, use "Email this Guest" and Switch to Template to send that email template.
I just put together a sample email template for you here: https://www.ownerrez.com/support/articles/template-receipt-billing-summary -- you can copy and paste that into the Custom Booking Template you create for this in your account. To paste, you'll need to hit Ctrl+V on your keyboard as browsers don't allow us to provide a paste button for security reasons.
