Just check your online account or app. It will appear on your account balance and your Payments once it has been paid to you. If you are a pay as you go customer, you will receive a voucher through the mail.
They don't appear to send any notifications.
Don't shoot me, I'm only the piano player. I DON'T work for or on behalf of EON.Next, but am willing to try and help if I can. Not on mains gas, mobile network or mains drainage. House heated almost entirely by baby dragons.