If you have a form that you don’t need and is not being used, you can delete it. Here’s how.
Go to Marketing Activities.
Find and select your form.
Under Form Actions, click Delete Form.
Remember to remove the form from any/all landing pages using it. Also, confirm that the form isn’t being used on a public website.
Confirm by clicking Delete.
If the form is being used on a Marketo landing page, you won’t be allowed to delete it. You have to go and remove it from whatever landing pages it lives on.
If you delete a form that is being used by your public website, you won’t see a warning and the form will be broken. Consider archiving it instead.