[solved] Coupon does not work correclty

Actually, not for me.

I installed
- Joomla 1.5.15
- Virtuemart 1.1.5

Configured in virtuemart
- checked Subtract payment before tax/shipping
- Vat of 20%
- Created a product of 500 without tax, 600 with
- Created a coupon of 20%

Results
- Subtotal 600
- Total 456
- Tax 80

This is all on a system that has never had AwoCoupon installed. The results do not even show you the discount, which is a bug that resulted from trying to fix the discount before tax problem of Virtuemart 1.1.4:
http://dev.virtuemart.net/redmine/issues/159

The fix for that is in
www/administrator/components/com_virtuemart/html/basket.php around line 256, change

<?php
$discount_after=false;
?>

<?php
$discount_before=true;
?>

When I do that, I now see a discount of 120, which is exactly 20% of 600. So the discount is correct, the total is off. While you are in the same file, if you change around line 258

<?php
$total -= ($_SESSION['coupon_discount'] * $my_taxrate);
?>

<?php
//$total -= ($_SESSION['coupon_discount'] * $my_taxrate);
?>

The total should come out correctly. I did this, and my total came out to 480. And I remind you, I never installed AwoCoupon on this site, this is just dealing with Virtuemart Coupons.

Taking your example, if you multiply the discount by the taxrate and subtract it from the total, as the line we comment out above you get
283.20 - (70.80*0.2) = 269.04
which is basically the total you are seeing. So hopefully, once you make the above changes, your shopping cart should look alot better.

Regards