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.
It will not compute if you are only viewing it on the form builder itself. You have to launch or preview the form to see the calculation totals.
I have checked your form, but I don't see any payment field, did you removed it? I suggest after adding the payment field try to preview the form to test the calculation.