STEP 1:
Click an invoice that is ready for approval and scroll down on the right side, you will see a button that says 'Notify the owner that the bill has been received.'

STEP 2:
When you enable this, the owner will receive a notification confirming receipt of the bill.

You can also clicked to 'Include Invoice Attachment' and then the owner will also receive the invoice PDF document with the email. They do not receive this by default unless this is setting is ticked.

STEP 3:
Once you click 'Approve,' this notification will send to your owner.