When it comes to refunds, Google's policy is that you have to fill out a specific form (attached below):
If you wish (and I would highly advise that you do) you can also attach one of our comprehensive reports regarding the fraudulent clicks done on your domain.
You can download the report by referring to your ClickCease dashboard:
Analytics tab--->Adwords sub tab.
Choose the wanted time frame uptop and scroll all the way to the bottom to the ad clicks table.
Click the Excel icon just above the table to download the report and attach it to your application.
That being said, we have now automated this whole procedure for you! Simply go into the tab called "Refund Claims" on the side bar of your dashboard and enable the function.
For more information, see here