@[deleted]You cannot set Custom Ticket Numbers by Department but you CAN set Custom Ticket Numbers by Help Topic. Help Topics are routed to Departments so I guess that's your workaround. Select a Help Topic (Admin Panel > Manage > Help Topics > click name), go to New Ticket Options, and set Ticket Number Format to Custom to make your Custom Ticket Number Format. Next, change Department to the Department you want the tickets created under the Help Topic to go to and Save Changes. Now once Users create a Ticket under the Help Topic it will be routed to the chosen Department and have your Custom Ticket Number.I hope this helps. Cheers.