We have a current issue where we are trying to apply a cart price rule to give 100% off for certain customers helping us get our site launched by giving us feedback. The problem is that when the grand total is calculated in the cart, the taxjar plugin is still applying a tax on shipping for qualified destinations based on the standard shipping cost even though the cost to the customer is $0.00 as a result of the price rule.

I have contacted TaxJar on this and while I've let them know I'm not satisfied with their response and opened a ticket/issue on their github to address the problem, their support is currently trying to pass the buck back to me saying I need to make a custom override to their code.

Seeing as how their initial response may bode that they won't enthusiastically try to fix this, I figured I would try just that (make my own override/fix) in the meantime. While they helped me find the point in the code where they are applying the tax to the shipping cost, it is obviously pulling the pre-discounted cost of shipping and I need to know where/how/what I can get the post-discounted cost of shipping. (the amount that is showing in the subtotal in the cart)

Any help is appreciated.

1 Answer 1


This is a bug with the TaxJar extension not properly passing shipping discounts to TaxJar's API when a shopping cart rule is applied to the shipping amount. It's being addressed in a pull request.

  • I had opened a ticket on your site at the same time I posted this. I also had a support email. They told me where to look in code and I suggested a fix which they implemented. It seems to have fixed the problem.
    – Scott
    Commented Jun 5, 2018 at 21:30
  • (I actually had trouble trying my suggested fix, but they implemented it anyway and suggested I try completely flushing my cache on client and server as they had tested it successfully. I had to flush everything including my cart but it did work)
    – Scott
    Commented Jun 5, 2018 at 21:31

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