At the moment it is not possible to know when a particular user completed the assessment, but you can set up email notifications for the assessment completions across your entire organization.
To do that, first go the “Account” tab in the bottom left corner, and select “View profile”.
Go to “Notification settings” tab and set up how often you want to receive email notifications regarding assessment completions in your organization - daily, weekly, monthly or never. You will then receive an assessment completion summary for the previous period to your email address.
Note: You will receive summary for all users in your organization, not just those you invited to complete the assessment. Also, if you have a UAC filter set up, you will only be notified for those users that match your UAC filter (for example, if you have a UAC filter set up for UK, and the user from Italy completes the assessment, you won’t be notified).