You can deactivate a license within the customer portal if you're a license owner or admin.
To deactivate the license you'll need to remove an identified user. To do this click on the Remove button alongside their details in the list. Then confirm the removal by clicking the Remove button to deactivate them.
A message will be displayed confirming that the user has been removed. This has the same effect as someone deactivating the product on their computer.
If a user has forgotten to deactivate the license on an old machine or their machine has crashed, you'll still need to remove them; when they activate their license on a new machine they are then added back to the list of users.