If you've invited a trainee and want to cancel the invitation because you've made an error, or the person has left and you want to invite someone else, you can. Note: this is different from deleting a trainee that you've added using the bulk upload or the add trainee form, this only works for pending invitations via email.
From the Course and trainee options menu, choose List trainees that haven't accepted an invitation. Click Delete next to the trainee whose invitation you want to cancel.