What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
At JotForm, we want to make sure that you’re getting the online form builder help that you need. Our friendly customer support team is available 24/7.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
You can review this user guide : How-To-Add-Coupon-Code-in-the-Payment-Form
But do take note that coupon code discount will only work for payment type that involves selling products.
It will not work of you are using Donation or custom amount payment type.
If you were using the method to pass the payment amount to payment field as described here , you may need to integrate your coupon code discount on the field/widget you used outside the payment tool.
I am referring to your thread here https://www.jotform.com/answers/1024319
Hope this help. Let us know if you need further assistance.