After you have created your subscription form and completed the basic setup, you may find it useful to add some more advanced settings, such as specifying that the form will be hidden from visitors who have already submitted it.
Let's see how you can do that:
1. Click on the Visibility Settings tab.
2. Scroll down to the Don't show the form to people who have already submitted it option and tick on the corresponding check-box.
From now on, your form will no longer be displayed to visitors who have already filled it out and submitted it.