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:

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

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

Hey Mike, I'm having the same problem, my accounting package (not MYOB) is giving an annoying 1 cent difference in GST calculations. Any luck on a fix?

No I didn't get a fix. Also, I'm now having problems getting the discount coupons of type Shipping to work correctly. The whole area of tax, discounts and order totals is a quagmire I can tell you. Sorry no help.

Hi Mike,

I don't have a solution, but I know why MYOB (and probably other acc packages) make the rounding error. MYOB rounds every line entered, and then adds these all up. In my case, I noticed this because our wholesale prices are 50% of retail, and our retail price is an odd number, so the wholesale price has 3 digits after the decimal (1/2 of 3.25 is 1.625). MYOB stubbornly refuses to take more than 2 digits after the decimal, so every line is rounded up half a cent.

This suggests a possible solution. Can you change the zen database so that the columns that hold totals only accept 2-digits after the decimal? Or maybe this has to be done in the php. That way, the figures you get out of zen would at least be equally wrong when compared to MYOB.

HTH

Rob

Thanks for the response. I'll have to check with a test order, but what you say makes sense. I think finding all the places in the code and or database that Zen Cart stores the running totals is making me queasy though, especially with regard to side-effects, and the impact on future upgrades. Maybe over the Christmas break!

Hi Mike

FWIW, I get around this by using the GST adjustment at the bottom of the invoice... mainly because it's easier and not every invoice comes out of ZenCart different to MYOB.

Do any of you have a program that imports sales and item details into MYOB? Thanks