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.
Yes, that is possible and quite simple.
What I would suggest is to check out the following steps: How To Add Coupon Code in the Payment Form
You will be able to see how to set up your coupon codes and the field for accepting the same will be added to your payment processor by itself.
Do of course let us know if you have any questions along the way and we would be happy to assist with the same.