Allow clients to close tickets

Currently, clients have the option to post a reply when checking the status of their ticket. However, it would be very helpful to allow clients to close/resolve tickets if they no longer need assistance. If a solution is sent and it works for them, why do I then have to go and read the reply then manually close the ticket?

Is there a mode for this? The 'allow clients to edit details' option doesn't provide this functionality unfortunately. I can't find any settings within the admin panel which would enable this function.

Is it possible?