Hi Nicolas,
In the Product tax category we have three options None, ITBMS, or Panama Default Tax Category (shown in screen shot). If I choose either ITBMS, or Panama Default Tax Category I get the tax worked out on the pre-discount amount.
All the products have a tax category of Panama Default Tax Category - so I think that using Panama Default Tax Category in the coupon is correct.
However the problem lays with the Apply discounts in the Configuration.
1. If I set Apply discounts to be before taxes (before taxes screen shot) the overall total is correct but the discount is wrong
2. If I set Apply discounts to be after taxes (after taxes screen shot the overall total is incorrect but the discount is correct
I would be more than happy for one of your team to log into my admin account and check why this mystery occurs in the set up
Regards,
Mike