You can delete fields, even if items have already been created that use that field. However, to delete a field, all objects must be edited so that they no longer contain references to that field. You can view references from the References tab when viewing a field. For a list of objects that can reference a field, see “Admin Provided Objects”.

You cannot delete a field that has historical references to that field in the history of one or more items. You must first delete the items that have entries for the field in their histories.