Calculation of tax on discounted amount

[Seldom_Seen]

Hi,

I have read through everything I have found on Discount hits. Have also tried to change the sort order of the output on my "Order Confirmation" page, but have so far not found a solution to my requirements.

 

osCommerce is version 2.3.1 and I have installed a Customer discount module that is working. But due to Norwegian rules and regulation the discount should be calculated on the amount without taxes.

What happens when the tax (14% on food) is calculated, i get the result based on tax calculted on the full amount, and NOT the discounted one.

 

Here is the calculations form my site:

(And this is how my potential client WANT to display this, so I cannot argue on this)

Sub-Total: $250.59

Customer Discount /27%) $67.66

Sub-Total-after-discount: $182.93

Flat Rate (Best Way): $20.14

14% MVA: $35.08 (Calculted on the discounted amount this should have been $25.61)

25% MVA: $5.04

Total: $243.19 (With calculation on tax on discounted amount the total would be $233.72)

 

I have tried everything I could possibly think of, but so far I cannot make this work.

 

If someone could give me hint or tips on how to change this I would be extremely happy and thankful!

 

Kind Regards,

Seldom_Seen.