You can set a form-wide limit on the total number of submission the form will accept. When the limit is hit, the form becomes inactive and we'll display the message “This form is no longer accepting submissions.” Clicking to the next page counts as one submission, so this works best with one page forms.
When you delete an entry, it no longer counts toward the limit. For example, if you set a limit of 50 entries, receive 50 entries, and then delete 2 of them—your form will be able to accept 2 more entries. If you were to delete all 50 entries, your form would be able to accept 50 more entries.
To turn off your form after a certain amount of entries: