What does this do?
On checkout if the Member hits the 'Add to Account' button it will add the cart items to any open invoice. If they don't have an existing open invoice it will open a new one.
Invoices can be closed out and charged at any time by an Admin in the Control Panel.
Auto Close Invoices
Invoices can also be scheduled to close on the 1st of the Month. Toggle on this feature in your settings.