How to add shipping and tax in a form

Kindly elaborate further on your question. I am going to assume you want to add tax and shipping cost to your Payment form. Below is a guide on how to add shipping:

https://www.jotform.com/help/304-How-to-Add-Shipping-Cost-to-Payment-Forms

Below is a guide on how to add tax:

https://www.jotform.com/help/296-How-to-Add-Tax-to-Your-Payment-Form

Hope the above answers the question. If not kindly send further clarifications on the issue.