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.
That's definitely one of Jotform's basic feature. You can set any fields "Required", even the payment fields so users can't leave it blank or simply they need to pay first before the submissions goes through.
So after configuring the payment field, here's how to make it required.
And here are the payment tools available.