[fixed 1.3.9a] Group Discount and Discount Coupon Tax Calculation Issue

[rlparker]

I have several different discounts running on my cart including quantity discounts and group discount

my tax is being calculated on the subtotal BEFORE any of the discounts and I need it to apply the discounts before calculating the tax

does any one have any ideas how I can do this or where the code is that calculates the tax?

thanks

Rachael

[swguy]

Using recalculate tax reduces the amount of tax based on the size of the discount. But the initial figure is based on the subtotal before discounts.

Be sure to get recent copies of Quantity Discounts and Group Discounts (the latter may involve upgrading your cart) - the tax logic has been refined over time.

[rlparker]

sorry this is probably a daft question but what/where is recalculate tax?

thanks

[rlparker]

if I set the discounts to recalulate the tax I am getting some very odd results.

Does anyone know what bit of code I need to edit to calculate the tax after the discount has bee subtracted?

thanks

Rachael

[psychicpet]

I am running 1.3.7 and am also having this problem...and on larger orders the discrepancy can be sizable.

Here is a sample order at 8.25% tax before application of a 10% coupon:

Sub-Total: $189.00
Shipping: $0.00

CA State Sales Tax: $15.59

Total: $204.59
=============================
The tax is calculated accurately. Now apply a 10% discount:

Sub-Total: $189.00
Shipping: $0.00
Discount Coupon: pc0108a10 : -$18.90

CA State Sales Tax: $12.47

Total: $182.57
=============================

The correct tax on a subtotal of $170.10 should be $14.03 but as you can see, the cart is calculating $12.47. I have had orders where I have lost as much as $6 in tax on an order.

Any ideas or fixes for this??

Robert

[nosnappyname]

Running Zen Cart 1.3.8a, Database Patch Level: 1.3.8

Similar problems to many here . Settings are :
Sort Order 190
(after sub total and before shipping)

Include Shipping false

Include Tax false

Re-calculate Tax Standard

Tax Class --none--

Error #1: Taxes on shipping are discounted even though Shipping costs themselves are not discounted. I do not want to discount shipping.

Error #2: The final total does not match the totals of items calculated after group discount is applied even after ignoring the error above. This is caused by a rounding error introduced through the method of proportional recalculation of the total instead of adding up the totals again.

Lastly, while it doesnt happen in my case due to a lucky choice of tax rate, the proportional method is at risk of causing rounding errors in the tax calculations too, eg
Original price = $5.00, tax excluded, group discount 10%, tax 7%.

1. (5.00-0.50)*.07=4.50 *.07 (7%) = .315 rounded up to .32 (the right answer)

2. 5.00 *.07 = .35 (original tax)
tax difference due to discount=.50*.07=.035 rounded up to .04
difference=.35-.04=.31 (the proportional answer)

So, when the rewrite takes place i hope these considerations can be taken into account.