When someone enrolls in your Program(s), they may have the option to enter a Coupon Code if you've created one and made it available for use in that Program (for help creating coupon codes, click here).
Transaction History
When a Coupon Code is used, the Discount Item you attached to it, along with the actual Coupon Code itself, will be displayed in the Transaction History in the person's Account.
Billing Page
When a Coupon Code is used, the coupon will also show under "Internal Billing Notes" on the customer's Billing page on the Enrollment Card.