In order to return a purchase made with Amex Pay, you will need to use the Card that has the same Device Card number used to make the original purchase. The last 4 digits of your Device Card Number can be found when you log into the Amex Mobile App, navigate to the Amex Pay feature and select your Card.
Please note that, depending on the participating merchant, you may not be permitted to use your plastic Card to return purchases made with Amex Pay. You also may not be permitted to use Amex Pay to return purchases made with your plastic Card.
You can also log into the Amex App and select the Card you used to make the purchase and hold your device near the contactless terminal at the merchant to process the refund.