Gregg, order invoices are send to customers at the end of transaction / payment for all completed orders. You can check how it works by logging out of your admin account and making a test purchase as customer.
Invoices are also send out to store owners, you can change how invoices are send out to store owners in SETTINGS -> Notifications -> New Orders.
The available options are: every order, once a day, once a week and never.
Steve - eez.io support