ZC Getting Sums Wrong?

Hi
Still using 1.3.7 I'm afraid but I have noticed in the past that there is the occasional 1p adrift in the total price on the invoice which I always assumed was in the rounding and lived with it.
But on this order it has failed to add VAT on one line, possibly due to its low value, but even then it doesn't account for the error in the total price.

The 'Total (inc)' on line 3 should be £0.58, but the overall total should be £9.97.

Where and why does ZC get it wrong?

Thanks
Pa

Just had another order with the total value a penny out.
Can someone at least point me to the php script that does the calculations so that I can attempt to work out whats going on?
Thanks
Pa

So I'm on my own with this one?

I believe most of this starts in includes/classes/shopping_cart.php...
I do not have to use VAT & have never searched for it so this may or may not be there???
You should also check includes/modules/order_total

Thanks for the response Kobra.

Done some searching around this forum and it seems like I'm not alone and this problem was reported months ago, affects lots of users, but sadly, no signs of a 'clean' fix yet.

The 'dirty' fix is to increase currency decimal places to 3 (or more?), but then the extra places show in the checkout, invoice etc. etc.

Hmmm .....

i have the same issue after i have quantity discounts installed

have you found a solution ?

I stand to be corrected on this but I understand the issue relates to this:

ZC calculates tax (rounded) on each individual item, then SUMS the total.

This is compliant with USA accounting principles.

In the UK and EU, tax is generally calculated on the total of the PRE-TAX amount - so, the UK/EU adds up the pre-tax amounts, gets a sub-total, then calculates the tax, and adds this to the pre-tax sub-total to get the grand total.

... all the while ZC calculates tax FIRST on individual items (rounded), rather than on the pre-tax total of all items, UK/EU users of ZC will get discrepancies...

It not only for a taxed amount where the the 0.01 error occurs.

Here is an example of the sub total + the postage = the total - 0.01

Zen Cart v 1.3.7