1. Log into your cPanel account.
click on the “Addon Domains” icon, In the “Domains” section.

chwkb-addon-domains-icon

3. place the addon domain beneath “Modify Addon Domain” and then click on the “Remove” link.

chwkb-remove-addon-domain

4. Press once again on the  “Remove” button.

You will receive a success message notifying you that your Add-on domain has been completely removed.