Prepare the transaction for a refund and get your Universal Analytics ID (looks like UA-xxxx-xx). Please notice, we use Enhanced Ecommerce for product refunds. It must be active in your account.
You may refund single products from any order (when it is partial refund) or you may copy paste transactions IDs.
Go to your Conversion - Ecommerce - Sales Performance overview in Google Analytics and you shall see refund transaction amount. You may also create custom view to check source/medium or campaign for your refunds and move your reporting to higher level.
Let us know at GetROI@marketingmakers.net