If you want to download an invoice to share with a student or for your own records you can do it through your Student Management Dashboard.
Use either the student search function or search manually through the membership or course that the student belongs to in order to locate them.
Click on the students name. You will then see a secondary menu with a menu item named 'Payment History'. Click on this menu:
From there navigate through the list of student transactions to the invoice you would like to download. Click 'Download' to download a copy of the invoice: