A ticket can be set to Closed status only in Edit ticket mode. If you try to close the ticket in Restricted ticket mode a popup message will notice that it is not possible and ask if you want to open the ticket in Edit ticket mode.
When you select Closed status the ticket is closed and normally a notification is sent to End User. If Global Configuration setting Mandatory to add a comment when closing ticket is enabled a popup is opened when you close the ticket. You must add a comment in popup to proceed and effectuate the closing. If Global Configuration setting Comment marked as solution is mandatory for closing ticket is enabled the checkbox Mark as solution has to be enabled for the comment (if other solution comment not exist).
If you select the comment in this popup to be Internal no closed ticket notification is sent to End User, so called Silent Close.
Close ticket comment popup
If the ticket has linked tickets connected there will be checkboxes in the form to:
•Activate that the comment should to be copied to all linked tickets.
•Mark the comment as solution also in the linked tickets. If any of the linked tickets has no solution comment and Comment marked as solution is mandatory for closing ticket setting is enabled, you have to enable this checkbox to be able to close the tickets.