[Done v1.3.9] Discount groups and tax calc problem with tax-included pricing

[srt9969]

Hi all,

Really sorry to post this again from e/where on the forum. http://www.zen-cart.com/forum/showthread.php?t=119602
It strikes me as an issue with the way tax is handled, but I need a view from a proper coder, as this facility is vital to my business. I'm sure it only requires a small alteration, but I'm struggling to find an answer:

I have a problem with group pricing and shipping (I think).
No Coupons
ZC1.3.8a
I set up a dummy product priced £100
I added it to the cart and checked out.
The cart shows:

Sub-Total: £100 (inc. VAT)

Shipping:£10.00 (inc. VAT)

Group Discount:-£5.00 (this is application of a group discount of 5%)

VAT 15%:£13.63

Total:£105.00


ot_group_pricing is set Include Shipping & Include Tax both False.

The VAT figure should be 105 * 15% = 13.70
What's actually happening is that the VAT is being calced thus:

104.50 * 15% = 13.63

The 104.50 is coming from:

100 less 5% = 95.00
10 less 5% = 9.50

The 5% is the group discount.

How do I stop the Group Discount being applied to shipping for VAT purposes? I guess it's in the tax module, but that code is a bit scary to a noob. Any help very much appreciated.

Thanks,

Sean

[wilt]

Hi,

This is a bug, and has been addressed in the upcoming v139 release.

There are a couple of files that need to be edited to fix this.

First is includes/classes/order.php

circa line 347 - you should see

                 'subtotal' => 0,
                        'tax' => 0,
                        'total' => 0, 

which should be changed to

                 'subtotal' => 0,
                       'shipping_tax'=>0,
                        'tax' => 0,
                        'total' => 0, 

next you need to edit includes/modules.order_total/ot_shipping.php

circa line 67 change

          $order->info['tax'] += $shipping_tax_amount;
          $order->info['tax_groups']["$shipping_tax_description"] += zen_calculate_tax($order->info['shipping_cost'], $shipping_tax); 

to

    $order->info['tax'] += $shipping_tax_amount;
             $order->info['shipping_tax'] += $shipping_tax_amount;
          $order->info['tax_groups']["$shipping_tax_description"] += zen_calculate_tax($order->info['shipping_cost'], $shipping_tax); 

and finally includes/modules/order_total/ot_group_pricing.php

circa line 60
change

    if ($this->include_shipping != 'true') $order_total -= $order->info['shipping_cost']; 

to

    if ($this->include_shipping != 'true') $order_total -= $order->info['shipping_cost'];
    if ($this->include_shipping != 'true') $order_total -= $order->info['shipping_tax']; 

Remember to backup any files you edit, in case of disasters.

[srt9969]

Hi Wilt,

Thanks for the reply. Unfortunately, it didn't work. It added 6 pence to my cart total, and subtracted the same from the group discount.
More to the point, it didn't affect the tax figure at all: I went on to try the same cart (product 100 in tax 15%, shipping 10 inc tax 15%) with a range of group discounts from 5 through 100%. The only one to figure right was (da-daaaa....) 100% discount. On some, the rounding was abominable, but that's a different issue...
Each conformed to the pattern: calculating the total tax on a figure derived from (Subtotal + Shipping)-((Subtotal + Shipping)*groupDiscount%), with no regard to how group pricing module switches were set.

It looks like I have to artificially raise my shipping prices, and set Include Shipping=true, in order to have the shipping discounted to the right price in the cart.
This is unsatisfactory as hell, as it misrepresents actual prices.
I love the functionality and adaptability of ZenCart, but I hate that it can't add up, or round out correctly.
I know this ain't your fault, or anyones, really, I'm just stunned that it hasn't been addressed long ago....

Here's hoping,

Sean

[wilt]

Hi,

My apologies, but it seems my fingers failed me.

Where I said to change includes/modules/order_total/ot_group_pricing.php to

    if ($this->include_shipping != 'true') $order_total -= $order->info['shipping_cost'];
    if ($this->include_shipping != 'true') $order_total -= $order->info['shipping_tax']; 

the second line should have been

if ($this->include_shipping != 'true') $order_total_tax -= $order->info['shipping_tax']; 

[wilt]

Note. The above is partly plagued by the rounding error mentioned in your other thread.

However I think I have a solution for that as well. Will post to other thread

[srt9969]

Aha!
And my apologies for not spotting the obvious and sorting it out myself...still on a heck of a learning curve

Sean