Just visit the Domains panel, and, under the "Registrar" column in the domains list, select the "Manage" button for the relevant domain to view its "Registration Details" page. In the "Actions" box on that page, you'll find an "Edit Renewal Type" option. Set this to "Do Not Renew" and our system will stop telling you about your expiring/expired domain to the maximum extent possible. (In typical "paternalistic bureaucracy" fashion, ICANN requires a certain number of notifications that you cannot disable or opt out of to protect you from yourself.)
