reopen thread [Done v1.3.9] Discount groups and tax calc problem with tax-included pr

[antonios]

Hello Wilt,

Here's what I'm trying to achieve.

First I should say I use two tax rates: 6% and 19%
Second I use discount groups, for loyal customers etc.
And third the shop displays prices incl tax.

When a customer in my discount group orders for €100.00 incl 6% tax this is what the calculation must look like:

Sub-Total: €100.00
Group Discount 30%: -€30.00
Shipping cost (incl 19%): €5.65
TAX 6%: €3.96
TAX 19%: €0.90
Total: €75,65

The group discount is subtracted from the subtotal with tax included, so the tax mentioned should be calculated after the discount is subtracted

When there are no shipping costs charged, the calculation is correct.
Even when a customer orders products with 6% tax AND products with 19% tax the calculation is correct (as long as there are no shipping costs).

Things only get messed up when shipping cost are charged.

Greetings Antonios

[antonios]

One thing I'd like to add:
When a customer orders products (any tax) and is NOT in a discount group the calculation is also correct, even when shipping costs are charged.

So it's clear that the problem is where there's a combination of shipping costs/tax and discount groups.

[DrByte]

And have you tried setting your Tax settings to NOT display the tax details split into multiple lines?

[antonios]

Yes I've tried that, also incorrect:

Sub-Total: €16.95
Flat Rate (Best Way): €5.65
Group Discount: -€4.82 (should be -€5.09)
tax 6% + tax 19%: €1.57 (total of tax seems ok, doesn't mean that the calculation is)
Total: €17.78 (should be €17.51)

Like I said, the problem isn't the difference in tax rates, but the combination of group discounts and shipping tax.

Greetings Antonios

[antonios]

I've been coding and puzzling , still no result.
If nobody knows how to fix this, I think I have to leave zen-cart for what it is and find webshop software that can calculate taxes etc.

What a mess and what a loss ..

[wilt]

Hi

Here's the patch/diff that I applied to Zen Cart v139d to fix the problem.

--- includes/modules/order_total/ot_group_pricing.php
+++ iincludes/modules/order_total/ot_group_pricing.php
@@ -61,14 +61,26 @@
 //    echo "order total = $order_total<br>";
 //    echo "order total shipping = {$order->info['shipping_cost']}<br>";
 //    echo "order total tax = {$order->info['tax']}<br>";
     if ($this->include_shipping != 'true') $order_total -= $order->info['shipping_cost'];
     if ($this->include_shipping != 'true') $order_total_tax -= $order->info['shipping_tax'];
+    $taxGroups = array();
+    foreach ($order->info['tax_groups'] as $key=>$value) {
+      if (isset($_SESSION['shipping_tax_description']) && $key == $_SESSION['shipping_tax_description'])
+      {
+        if ($this->include_shipping != 'true')
+        {
+          $value -= $order->info['shipping_tax'];
+        }
+      }
+      $taxGroups[$key] = $value;
+    }
     if ($this->include_tax != 'true') $order_total -= $order->info['tax'];
- //     if ($this->include_tax != "true" && $this->include_shipping != 'true') $order_total += $order->info['shipping_tax'];
+     if ($this->include_tax != "true" && $this->include_shipping != 'true') $order_total += $order->info['shipping_tax'];

     $orderTotalFull = $order_total;
 //    if (DISPLAY_PRICE_WITH_TAX != 'true') $order_total += $order_total_tax;
 //    echo "order total* = $order_total<br>";
-    $order_total = array('totalFull'=>$orderTotalFull, 'total'=>$order_total, 'tax'=>$order_total_tax);
+    $order_total = array('totalFull'=>$orderTotalFull, 'total'=>$order_total, 'tax'=>$order_total_tax, 'taxGroups'=>$taxGroups);
     return $order_total;
   }
   function calculate_deductions($order_total) {
@@ -77,6 +89,7 @@
     if ($order_total == 0) return $od_amount;
     $orderTotal = $this->get_order_total();
     $orderTotalTax = $orderTotal['tax'];
+    $taxGroups = $orderTotal['taxGroups'];
     $group_query = $db->Execute("select customers_group_pricing from " . TABLE_CUSTOMERS . " where customers_id = '" . (int)$_SESSION['customer_id'] . "'");
     if ($group_query->fields['customers_group_pricing'] != '0') {
       $group_discount = $db->Execute("select group_name, group_percentage from " . TABLE_GROUP_PRICING . "
@@ -104,11 +117,11 @@
           }
           $adjustedTax = $orderTotalTax * $ratio;
           if ($order->info['tax'] == 0) return $od_amount;
-          $ratioTax = $adjustedTax/$order->info['tax'];
+          $ratioTax = $adjustedTax/$orderTotalTax;
           reset($order->info['tax_groups']);
           $tax_deduct = 0;
-          foreach ($order->info['tax_groups'] as $key=>$value) {
-            $od_amount['tax_groups'][$key] = $order->info['tax_groups'][$key] * $ratioTax;
+          foreach ($taxGroups as $key=>$value) {
+            $od_amount['tax_groups'][$key] = $value * $ratioTax;
             $tax_deduct += $od_amount['tax_groups'][$key];
           }
] 

[antonios]

Wilt!
You've just made a girl extremely happy!

It works like a charm, with and without tax split lines, with and without shipping costs and with multiple tax rates.

Thank you, thank you, thank you.

I hope the zen-cart team will add this patch to their next update.

Greetings Antonios

[mooomers]

strange.. i put in the changes from your diff, and it's calculating the discount wrong. and the tax is also still wrong.

What did i screw up?

The discount is 20%

Your Total

Sub-Total:$82.50
Group Discount:-$17.00
Canada Post (Expedited, 2010-07-13):$9.59
13% HST # + 13% Shipping HST #:$10.08
Total:$85.17