When discounts are applicable for a product, in the Invoice Product form we see that the tax is being calculated  excluding the discount. This results in an incorrect Tax and Extended Amount.

On an invoiceproduct, CRM calculates the tax and extended amount automatically and it doesnt seem possible to intercept through a plugin for setting a different value.

Is there a work around for this?

In my example, here Discount is 10%. So the Amount = £90 is correct. However, I expect the tax to be £18 and the Extended amount to be £108.