Sales Tax incorrect when using Discount Coupons

[twiddletails]

I've read all the threads on this but still haven't found a solution.
I'm running V1.3.8
In King Co, WA state the sales tax rate is 9%
When a customer is using a discount coupon, however, the sales tax is calculated incorrectly. I have not been able to figure out how Zen Cart gets to the total it calculates.

Example:
Order total: $7.72
-30% coupon: $2.17
+ Shipping: $2.25
Sub total: $7.80
Tax (9%): $0.59 (Should be: $0.70)

I'm sure I just have a setting incorrect but haven't been able to fix it.
My discount coupon module is set as follows:
Include Shipping: FALSE
Include Tax: FALSE
Re-calculate tax: STANDARD

Please help!

[Mushez]

Hi,

Had the same problem solution is in "Modules" - then "Order Total"

In there it sorts which order zen cart calculates everything for the order and often is set up that creates problems with sales tax used with coupons.

Work it out and re-set the sort order to make it work right for your needs and you will be away laughing.

[cdelab]

Hello,

I also have the same problem and I made many tests and never get both the good price AND the good VAT

So can you give me (us) details about the solution you find?

My parameters are :
-All price are displayed VAT included (gross price)
-Coupons in % or € are based on sales price VAT included

For example for a 10€ coupons :
-customer buys an article : 100€ VAT included
-use the coupon : -10€
-Total price is : 90€ VAT included

Based on that final price I want to re-calculate the VAT : 90 * (VAT/1+VAT).
Assuming a VAT of 19,6%=0,196 the result must be 90*(0,196/1,196) = 14,75€

Then I want to display:

Article x1 : 100€
Coupon : -10€
Total : 90€
VAT 19,6%: 14,75€

Are you able to help me to get this result.