When it comes to refunds, Google's policy is that you have to fill out a specific form (attached below):
Google allows the submission of this form once every two months.
We've now automated the submission process for you!
As part of our Standard and Premium services, the system will now automatically submit these refunds claims for you every 2 months.
Furthermore, not only will it submit the application for you, but it will also attach our comprehensive ad clicks reports to it for the recorded last 2 months.
All you need to do is click the "Tools" tab and then the "Refund claims" sub tab.
Choose "Enable" in order to opt in to this service.
You may still submit the reports manually by downloading the report yourself in the same page.
That being said, statistically speaking, Google refunds about %20 of all refund applications submitted to them and of those %20, only about %12 of the claim is actually refunded.
That is why actively blocking click fraud is a much better practice that will save you a lot more money in the long run.
Please note that this service is only available to STANDARD and PREMIUM plan customers and requires an active connection to your adwords account.