tax GST one cent and MYOB
If I compare Zen Cart order values with those calculated by MYOB, or those calculated in MS Excel (two ways; one by total then round, one by round then total) then the Discount, GST and Total values can be out by up to 3 cents. Sometimes they are the same.
After some thought, I figure that there are so many factors of precision, rounding, timing and sign value, and regulations, that the totals are never going to be guaranteed to come out the same as we the shopkeepers 'calculate'.
I suppose the crux of the issue (except where there is a bug) is that if I want to produce order confirmation emails, and show account history, and have those values reflected in the sums I take out of the customers' accounts (I authorise on order and debit on shipping) then if I produce the invoice and or packing slip from another application (in my case MYOB), then I should expect the likelyhood of discrepancies.
However...
Here's a good 10% discount (excluding shipping) example with 12.5% tax:
[FONT="Courier New"]
___EX GST##########__INC GST##########___gst
Goods
$480.0000##########$540.0000___$60.0000
_$25.5556##########_$28.7500____$3.1944
$250.6667##########$282.0000___$31.3333
_$29.1111##########_$32.7500____$3.6389
__$8.4444##########_$88.2500____$9.8056
---------------------------------------------
$863.7778##########$971.7500__$107.9722
Shipping
_$32.7100##########_$36.7988____$4.0888
Discounts
__EX GST##########INC GST##########___gst
$48.0000____$54.0000____$6.0000
_$2.5556##########$2.8750____$0.3194
$25.0667____$28.2000____$3.1333
_$2.9111##########$3.2750____$0.3639
_$7.8444##########$8.8250____$0.9806
-------------------------------
$86.3778____$97.1750___$10.7972
Here's the analysis of the differing calculation results:
##########____XL (add-round)_XL (round-add)##########__MYOB____Zen Cart
Sub total##########__971.75####################971.75##########874.59##########_971.75
Freight####################36.80####################_36.80##########_36.80##########__36.80
Discount##########____97.18####################_97.19##########_97.16##########__97.18
GST####################___101.26####################101.28##########101.27##########_101.27
Total####################_911.37####################911.36##########911.39##########_911.38
[/FONT]
FWIW I think the first XL column is the most accurate, with $97.18 being a fair rounding of the 10% discount on $971.75. That means the Total should be $971.75 - $97.18 = $874.57 (see MYOB is two cents out). Add on the freight of $36.80 = $911.37 as shown. Tax on that is $911.37 / 9 ( a benefit of 12.5% tax rate) = $101.2633333 which has to be $101.26. For some reason, ZC has one cent moved between the Total and the GST, probably to do with the underlying value of the discount? So I think Zen Cart is 'wrong'. What do you think?
The problem is, how to deal with this?
Firstly, can anyone tell me if there are known bugs with off-by-one-cent errors in order_totals with or without discounts etc, in 1.3.6, and if so, how to fix them? I have already made a couple of changes as discussed here
Secondly, can anyone offer me help to get my ZC figures to come out as per my MYOB figures every time, or visa versa, or does anyone know specifically why they do not? (I saw DrByte's post explaining the round-then-add strategy)
Failing that, Has anyone modified the Invoice and or Packing slip to be print friendly and include shipping instructions, or other relevant data?
Since the Invoice and Packing Slip pages in ZC Admin do not show Shipping Instructions for example, do show customer email addresses, and given that there is no Print Friendly option, I can't see that these are meant to be used unchanged. I had always planned for the ZC admin generated stuff to be the confirmation and record of the order (by email and account history, and these are more than adequate) but that my accounting and shipping would be done from MYOB. Now I am sitting here wondering how to reconcile the two; I can't seem to force MYOB to record values that I obtain from my ZC order....
Help and guidance very much appreciated at this stage!
Mike
Last edited by bikemike; 23 Nov 2006 at 02:11 PM.
bikemike
'If language is not used correctly, what is said is not what is meant. If what is said is not what is meant, what ought to be done remains undone' Kǒng fū zǐ
Bookmarks