When you are deleting or removing addon domains from cPanel, it important to remember that the cPanel automatically creates the folder where the website files are saved. If the folder is also a subdomain of the primary domain, then you may need to remove the subdomain before you can delete the addon domain.

To delete or remove an addon domain from cPanel, please do the following steps:

1. Login to your cPanel.
2. click Addon Domains in Domains Section.
   
3. Scroll down to the bottom, under Modify Addon Domain, find Actions, click Remove.
   

Note: Deleting or removing the addon domain only removes the domain from the DNS and server configuration. Your files and databases are not deleted or affected by removing the addon domain (other than the fact that you can not access the affected files via that deleted or removed addon domain name).

If you want to know how to add addon domain from cPanel please Click here.