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.
The Payment Tools do not have their own inventory managment module. So it will be difficult to have this feature using only the Form Builder.
However, you may want to use the Inventory Widget instead and combine it with the Payment Tool to have inventory functionality and payment/order function as well.
Here is the demo Inventory Form you can test http://form.jotformpro.com/form/51413853223953?
If you submit the form, you will see the invenroty available balance get updated.