Be logged in, use the deletion link which will take you to the Settings page. Halfway you’ll see the deletion option. Everything will be deleted.
URLS:
http://www.simplenote.com/
https://simple-note.appspot.com/settings
Please note that AccountKiller.com is not associated with the business listed on this page. AccountKiller provides easy-to-understand instructions and guides on how to cancel charges and relationships from the list of businesses on our site, we have no affiliation with these businesses.