Hi, I've got a coupon for my business out currently that is restricted to certain items.

The coupon is supposed to discount a certain items 10%, which it does, however, when purchasing an item with the discount at the same time as an item without the discount, it discounts the tax 10% for the whole order.

Example.

item 1 $20.00 (non-discounted item)
item 2 $10.00 (discounted item)

subtotal $30.00
discount $1.00
Tax(5%) $1.35
Total $30.85

Here, the tax SHOULD be 1.45, because the discount should come off the subtotal, and then be taxed. However, instead, it is discounting the one item 10%, then discounting the tax value for the complete order, including non-discounted items.

It is kind of confusing, but i am unsure of what to do and wondering if this is a common problem.

Thanks