Coupon Codes in Coupon Reach are typically used in conjunction with Client Portals.
In the software, Coupon Codes have a merge tag that can be placed on a Coupon Page as well as on the message where the same coupon is used. If you edit a coupon page, go to Step 2 and open up or place a Page Content, you'll see a "Coupon Code" button below the text box which is basically for its merge tag:
You can also see the same coupon code merge tag along with the merge tags in campaign messages such as the Immediate Message, Reminders, etc..
The Coupon Code is used, for instance, when the customers need the business staff to redeem the coupon for them (both onsite at the restaurant as well as online ordering deliveries). The staff will need to use a Client Portal to redeem the customers' coupons. For example, when customers subscribe and receive their coupon with the coupon code on it, they can show the coupon or just tell the coupon code to the staff. The staff can then open up the client portal and input the coupon code there. They can then manually redeem the customer's coupon for them.
The same thing also works for online ordering (on-call), where the staff can ask for the customer's coupon code during the call, and redeem it for them.