Just like everything else with the IRS, sales tax calculation can be a nightmare, particularly for ecommerce merchants. Sales tax numbers vary by zip code and change frequently.

Fortunately, most shopping cart packages already have built-in sales tax calculators. When the customer places an order on your website, based on their zipcode, the shopping cart will automatically do the math for you.

However, if you want to do your own lookup on sales tax by zipcode, here are two easy tools.

Disclaimer: I have not used either of these tools for any serious calculation. I have only played around with them and the answers seem right to me. So this is not an endorsement of any sort.

  1. Zip2Tax – These guys offer a web-lookup service for a monthly fee, and they also sell Sales Tax Tables for a one-time fee. They claim that –
  2. Every month each state is analyzed carefully by our tax experts for changes to both the tax rates and the ZIP codes. Our data is updated and provided to our subscribers on the first of every month. Tax table Updates are provided to subscribers a couple of days before the beginning of the month to allow time for implementation.

  3. Here is another way to lookup sales tax percentages. Use the Wolfram Alpha search engine. Type in your Zipcode followed by the phrase “sales tax” and it will show you the answer. For example.