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.
There's a way to prevent users from using the same coupon code again. Just set that same field as the Unique Question on your form.
To do that, click PREFERENCES at the top of your FORM BUILDER > ADVANCED tab > then select the Coupon code field as your UNIQUE QUESTION.
Complete guide: How-to-set-Form-Limits-Based-on-a-Unique-Question