In cases when you can't deactivate a user, such as a user being selecting in a custom hierarchy field, freezing the user is an option. Freezing a user prevents them from logging in to the organization while you complete the necessary steps to deactivate them. To freeze or unfreeze a user, follow the steps below.
1. Navigate to "Setup": In order to freeze or unfreeze a user, you must first select the gear icon in the upper right corner of your screen and then click Setup.
2. Navigate to the Table of Users: In the new window/tab that opened, type "users" into the Quick Find box and then select Users. 
3. Select the user you want to freeze or unfreeze.
4. Click the "Freeze" or "Unfreeze" button.
Notes
- This process is the same for both freezing and unfreezing a user.
- Freezing a user does not make their licenses available for other users. Only deactivating a user will make their licenses available.
