In Administration Console Dashboard under Administration Tasks, click User Devices.
Select the Identity Server cluster that contains the user.
If you want to search for the devices belonging to a particular user, enter the user name in User.
Alternatively, browse the list of devices Administration Console displays.
Click the Delete icon next to the device you want to deregister and click OK.
After a mobile device has been deregistered, it can be registered to a new user. However, MobileAccess on that device must first be reinstalled. See Deleting and Reinstalling the MobileAccess App on a Device.