There are several places to see this information. If you have registered and not paid, there will be a red window at the top of the Dashboard indicating "Payments Due" . The feis is listed with an amount.
If you return to the Register area, the Cart will list all event registrations, feis fees and any credits. If there is a Balance due, it will be listed as a Balance and the Make a payment button will be active.
At the bottom of your Dashboard will be a Recent Payments window that will list what type of payment was made, for which feis and how much.