How my customer used the one-time coupon twice on the same subscription. How to prevent this from happening?

Problem Statement

A customer used a one-time coupon more than once on the same subscription. You want to prevent this.

Solution

One-time coupons are marked "Exhausted" after use and are not reapplied on renewal. In the admin UI, they cannot be added again. In the portal, if customers can "Add/Remove coupon," they can remove and re-add the same coupon, effectively using it twice.

To prevent reuse:

1. Revoke add/remove coupon access – Disable the option for customers to add or remove coupons in the portal.
2. Use coupon sets – Create coupon sets and give each customer a unique code. Once a code is used, it cannot be reused.