error in tax calculation

I’m not an accountant or anything but I think this is an issue, especially if you have an accountant and they want all the numbers to match properly.

ItemX = $15.00

Purchase quantity 2.

Total Price $30.

Suppose the tax is 8.1%. Now you’d think the tax would be $30 * 0.081 = $2.43, but I’m getting a tax of $2.44

I think I know where the issue is coming from:

$15 * 0.081 = $1.215, rounding to 2 decimals: $1.22

$1.22*2 = $2.44

UC should store more decimal places on the backend, I’d say 4 would be enough to catch this issue. Though I have looked in the serialized items in the db and they are stored at about 32 decimal places (nuts huh).

I’m integrating the orders into a MS Dynamics GP server (no easy task) and issues like these give many errors.

It’s also rather confusing that when calling fn_get_order_info the subtotal includes tax, but on the page subtotal doesn’t include tax.

This has been discussed repeatedly over the years. At least ‘tax system improvements’ is now a planned item on the updated roadmap; the rounding errors should have been addressed a long time ago.


I just found another error in tax I believe:

subtotal: $30.00

shipping cost: $14.22

Including discount: $10.00

Order discount: $3.00

NV Tax (8.1%): $3.59

Note the tax is $3.59

shipping tax = 14.22 * 0.081 = 1.15
product tax: 30 * 0.081 = 2.43 -> 2.44 in their case

1.15 + 2.44 = $3.59

But what about the Order discount of $3

27 * 0.081 = 2.187 = 2.18

So the tax should be $3.33

That is a huge issue, much more significant than that rounding error issue.

[quote name=‘phazei’]I just found another error in tax I believe:[/QUOTE]

This has been reported in the following Bug Tracker post:


Still MIA. I am guessing (hoping) it i part of the tax system improvements.