You can ban a user account, so the banned user can no longer access YouTrack to perform any operation.
Banned users are not counted as active users for license restrictions.
If, for example, you have a license for 10 user accounts and already have 10 registered users,
you can ban one account and create a new one. Of course, that's not the only case for banning a user, but one of the most useful.
To ban a user account:
In the Users list, select the user accounts that you want to ban.
Click the Ban button in the toolbar.
The selected accounts are banned immediately.
You can unban previously banned accounts at any time.
To unban a user account:
Select one or more banned accounts in the Users list.