In order to request a refund from Google Ads based on the data on suspicious and fraudulent ad clicks, you have to fill in their click quality form available here to request a manual investigation on their end.
The form requires a click log to be submitted. You can easily obtain the data from ClickGUARD by logging in and visiting Click Reports > Clicks. There you can filter out the time period for which you're requesting a refund, include suspicious and/or fraudulent clicks and apply any other filters and then click on the green download icon to get the CSV file you can submit with the form.
Important: You can request a click quality investigation once in every 60 days.
You can (and likely should) configure a click quality report email within your ClickGUARD Settings to be sent to you every 2 months:
You can use the information provided within the email (including a link to download the click log) to easily fill out the form. It comes down to copy & paste.