Refund a Fulfilled Order
First, login to Marketplace using your credentials. Once logged in you will see a menu like this on the top left.
Click on the merchant name you need to go into. In our example, that would be Chess Program. Open the arrows until you get down to the store you need and you will see a listing called Fulfill Orders. Choose that option.
This will open up a dialog to search for fulfilled orders. So choose a date range that makes sense for the order you are looking for and on the drop-down at the right choose Fulfilled Date, then click on the button below labeled Search (Note that there are two buttons labeled Search, use the top one.). If the know the order number, you can skip ahead and use the Search by Order below the date range search option.
Next you will presented with a generated list of orders that meet your search criteria. Find the order you need and click the link titled View on the far right.
Next, the screen will show the entire order for just that order. Scroll down until you find the drop-down asking for the New Quantity to Return and choose the quantity you want to refund (usually this would be 1). Then scroll down until you find the purple button labeled Process Refund and click that.
One more little confirmation window should pop up asking if you are sure you want to continue. If you click OK, the refund will process right then.
That's it, you are done.