Push a window.postMessage event to the parent window for iframed Pardot forms. You can then intercept this message via Google Tag Manager (see: X) for an example.

pardot-form-submission-postmessage-event

<script>
if ( window.parent.postMessage ) {
  window.parent.postMessage({
    'event': 'Form Submission',                                              // Never change this
    'form_id': '1234',                                                       // The Pardot form ID (you can get this from the form edit page URL)
    'form_label': '[Whitepaper] - The 2020 State of Digital Accessibility',  // This can really be whatever you want.. but make sure its descriptive
    'form_action': 'Gated Resource Download'                                 // See suggested Form Actions
  }, '*');
}
</script>

You can find the your pardot form ID by navigating to the specific form details page inside of the pardot interface.

For example:
https://pi.pardot.com/form/read/id/1418

The form ID for that form would be 1418. This ID will never change for the lifetime of that form. Which is helpful for being able to track it down inside of pardot when looking at event reports inside of Google Analytics.

Suggested form actions:

Service Inquiry
If the form submitted is related to a particular service you sell.

Product Inquiry
If the form submitted is related to a particular product you sell.

Demo Request
If the form is to request a demo (either on-demand or 1:1).

Trial Request
If the form is to request a trial.

Contact Request
More generic forms that aren't specific to a particular service/product.

Gated Resource Access
E-Books/Whitepapers/Case Studies/Infographics/Reports/Guides/Video etc… Basically any downloadable resource where a form submission is required.

Webinar Registration/Replay
We split out webinars into their own action because they're a bit different than gated video you would typically place under resources.