[DUG] MYOB Rounding Issue - MYOB Data File Attached

[Cheng Wei (FMI)]

Hi Paul,

This is very enlightening, with flowthrough accumulated rundoff it is
guaranteed the overall rounding is always within half a cent. This will
guarantee a consistent result in both systems.

Awesome, we'll try this.

Many thanks.
Cheng

|-----Original Message-----
|From: Paul Heinz [mailto:paul at accredo.co.nz]
|Sent: Friday, 12 November 2010 1:00 p.m.
|To: Cheng Wei (FMI)
|Cc: NZ Borland Developers Group - Delphi List
|Subject: RE: MYOB Rounding Issue - MYOB Data File Attached
|
|Hi Cheng Wei
|
|> Please find attached a zip file containing:
|>  
|> - A company data file (AccountRight Enterprice v19+);
|> - A sample invoice pdf generated by our system;
|> - An MYOB Item Sales import file generated by our system, containing 
|> line items of the invoice.
|> 
|> Invoice Number: GR2115
|
|Very interesting. As it turns out, from that invoice it would appear 
|that MYOB uses the same GST rounding model that we use in our product, 
|Accredo.
|
|Our algorithm is a line-by-line GST calculation rounding to nearest BUT

|with flowthrough accumulated roundoff. The result of this algorithm is 
|that you get exact whole cents on each line which is ideal for 
|accounting analysis but the resulting total GST is also consistent with

|rounding the whole document total just once.
|
|To get an idea of how this algorithm works on a line by line basis:
|
|The 1st line is $272.16, add 15% = $312.894, rounds to $312.89 and 
|0.004 difference.
|
|The 2nd line is $28.88, add 15% = $33.212 + 0.004 diff = $33.216, 
|rounds to 33.22 and -0.004 difference.
|
|The 3rd line is $80.00, add 15% = $92.00 - 0.004 diff = $91.996, rounds

|to $92.00 and -0.004 difference.
|
|The 4th line is $589.50, add 15% = $677.925 - 0.004 diff = $677.921, 
|rounds to $677.92 and +.001 difference.
|
|The 5th line is $58.95, add 15% = $67.7925 + 0.001 diff = $67.7935, 
|rounds to $67.79 and +0.0035 difference.
|
|The 6th line is $60.55, add 15% = $69.6325 + 0.0035 diff = $69.636, 
|rounds to $69.64 and -0.004 difference.
|
|The overall GST total = $163.51.
|
|Note that this result is the same as taking $1090.04, add 15% = 
|$1253.546, rounds to $1254.55 and -0.004 difference.
|
|In each of the above examples, I'm showing the inclusive total which is

|how MYOB stores it per invoice line but you can also just calculate GST

|at 15% and round that with the flowthrough model which is what Accredo 
|does since they are mathematically equivalent.
|
|I'm not sure if MYOB also handles negative documents consistently and 
|rounds exact half cents _down_ for credits which is something we also 
|factor into the algorithm in Accredo.
|
|We like our negative invoices to give the exact same figures as an 
|equivalent positive invoice with just the signs flipped.
|If you use standard IEEE round-to-nearest, you won't get that for 
|documents with lines that have exact half cents of GST.
|
|I'd need an example of an equivalent credit document to confirm MYOB's 
|behaviour in that case.
|
|Cheers,
|  Paul.
|
|
|
|
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