Only an organization manager has the right to delete an organization.
It is necessary to first remove all members of the organization via the organization's administration pages.
Select all members
For the selected members, click "Remove this person from your organization"
The manager, being the last person left, must then click on the button "Leave the organization", located at the bottom of the portal homepage.
Note: This action is not permitted for organizations with Premium offers.
You will need to contact client support (firstname.lastname@example.org).