You can mark a fraudulent order "Fraudulent" in your Store Manager in order to remove it from your revenue share calculation.
After you receive an order, you have 90 days to mark it "Fraudulent." Billing for revenue-share occurs on a monthly basis, so if you've already been billed for revenue-share that includes an order you've since marked as Returned, Cancelled, or Fraudulent, a credit will be applied in the next month's billing. To do this, take the following steps: