Posted 04 April 2012 - 11:05 AM
I use zip code based sales tax calculation on my site and I'm finding that the site is over charging the sales tax by a few pennies. I'm very confused with this. I've double checked everything and the formula entered is correct, the zip code tax rates are correct, yet the site consistently miscalculates the sales tax. Am I missing something?
Here's the formula used:
Sales Tax = [Zip Code Rates for CO]% * (Sale Price - Discount)
$0.27 = 2.9% * (8.85 - 0.00), should have been $0.26, actual calculation is $0.25665
$2.16 = 2.9% * (73.85 - 0.00), should have been $2.14, actual calculation is $2.14165
the zip code tax rates are setup so that all of Colorado charges 2.9% unless it is within Larimer County which charges 3.7% unless it is within the city of Loveland which charges 6.7%. Again, I have verified the tax rate table is correct and have tested that it comes up with the correct tax rate for the various zip codes. The formula is correct as well and I just don't see how the site can calculate the tax incorrectly. This can be a really big problem for me if someone complains that they are being overcharged on sales tax.
Any ideas on what is happening?