Ah, thank you so much. Yes, I knew the figures were correct but my aim is to have total show the actual total charged (so after the discount is subtracted) and the tax line show the amount of tax included after the discount. There is no discount on tax itself, as you said, but after the goods are discounted there will be proportionally less tax, and I believe the local tax man requires this to be displayed correctly! :-)
I will adjust the order as you have indicated, and see how it goes from there.
Thank you again!