Any circumstance that prompts you to discontinue Zoho CRM service or delete an unused account you can delete the CRM account. Similarly, if an employee is no longer using the org CRM account you can either deactivate or delete it. 

Points to note before you delete CRM account:

1. You can delete a single user or personal account immediately, provided it is subscribed to Free edition or on a trial edition.
   
   
2. If you are subscribed to a paid edition, you must first downgrade to free edition or cancel your subscription.
   To downgrade from a paid edition:
   
   
1. Click on the Profile Icon
   
2. Go to Manage subscription
   
3. Click on Change edition
   
4. Switch back to free/Move to free edition.
   
   
3. If the account has multiple active users, before deleting the account you must deactivate all the users except the super admin.
   
   
4. Once you have downgraded to the free edition of Zoho CRM and have only one user left, i.e; Super admin you will get an option to delete your CRM account.
   
   
5. If required, you can take the entire data back up of your account's data and attachments. 
   

To delete your account

1. Go to Setup > General > Company Settings.
   
2. On the Company Details page, Scroll down
3. Click the Delete CRM account button.
   
   
4. Read the warning message and confirm the action.
   You will be logged out of your account and a system generated email regarding the account closure will be sent to you.