Company Administrators have the option to revoke invitations sent to users as long as the invitation status is listed as 'Invited'. To view all invitations and their status, click 'Invitations' on the left. Invitations can be revoked by clicking the red bin symbol to the right of the entry.
What happens if the user tries to register via the invitation after it was revoked?
If an invitation has been revoked and the user clicks the 'Accept invite' link in the invitation email they receive, they will be presented with the following screen and will be unable to register under that company: