Tax Calculation is incorrect

I am also experiencing the same issue with incorrect tax calculation from the payment widget after a discount/coupon code is applied. Instead of calculating tax at the discounted price the tax calculation is being calculated at full price i.e. ( Let's say I have a $25.00 off discount code/coupon and am applying a discount to an item priced at $100.  The tax rate is 9%. it's calculating the tax at full price which in this case is $100.00 and not $75.00)

Hello, can you please confirm if this is the form you're currently working on?

https://www.jotform.com/70398520063151

I'm asking because the scenario you described is different from how that form's Purchase Order payment field was setup:

1. The payment field doesn't have any Coupons

2. The Base Tax Rate set is 8.5%

With these 2 above, the form works as intended (adding 8.5% to the total):

If it's a different form, please share with us the Form URL/ID. In case we misunderstood your question, just get back to us with a bit more info and a clearer description of what you're trying to do so we can better assist you.