Tax Role goes by product not by customer role in B2B partner portal

We do have different type of customers, some of them are tax-exempt customers, when you apply tax-exempt role on the customer level, it dosent refect the tax exempt on dear partner portal, but when you apply te tax-exempt on the product level, it does reflect no tax! can you help with activate the tax exempt on customer level not produt level, as if we do it with product level, this will apply to all customers, not only one!

Please let me know at your earliest convenice as this is a critical issue!