Google has recently begun providing Google Product Search users with information on the tax and shipping costs of items in the U.S.

Users will now be able to see tax and shipping cost displayed alongside the product listings for which merchants have submitted this information. Google says that by providing this information it is a good way to maximize the visibility of your products during the holiday shopping season. It also helps buyers when they are making purchasing decisions.

The Google Base Help page explains how to submit information.

You can submit this information in two ways:
1. Set account-level default values in your Google Base account: These preferences will serve as the default values for all of your items. This is the easiest way to set up tax and shipping for your account.
2. Include item-level override values in your data feeds or via the Google Base API: These values will override your account-level default settings for that item.
To submit tax information there are three options.
1. Opt to not charge tax.
2. Set a tax rate based on the state an item ships to.
3. Use an estimate based on the destination ZIP code. Note: To estimate the tax rate, we use data from Tax Data Systems based on the destination ZIP code.
For shipping there are also three options.
1. Specify a flat shipping rate (or free shipping).
2. Define custom tables if the shipping rate you charge varies by price, weight, or number of items. Note: If you define a table based on the number of items, for now, we’ll use the rate in the first row only.
3. Apply a carrier-calculated rate if the shipping rate you charge is based on rates from UPS, FedEx, or USPS. Note: We use daily rates for UPS, and standard (non-retail counter) rates for FedEx.

Google also has tips for Google Product Search merchants.

From the Google Base Blog: Include unique product identifiers: In addition to using our five required attributes, be sure to include the recommended attributes relevant to your products, such as product identifiers like MPN, UPC, or ISBN. By including these, you’re giving us more information to help us include your products on Google Product Search product pages (our merchant comparison pages) when multiple merchants are selling the same product.

Use effective titles: There’s nothing like an accurate title to tell shoppers at a glance exactly what you’re selling, so be sure to use detailed and descriptive titles for your products. Do keep in mind that Product Search truncates titles to under 70 characters, so avoid exceedingly lengthy titles.

Write accurate descriptions: Descriptions offer an overview of the product you’re selling, so make sure that your descriptions are accurate and more than a few words in length. But if your descriptions are over 150 characters, you may want to shorten them to only include the most crucial information, as Product Search truncates longer descriptions.

Submit your feeds frequently: Lastly, remember to submit your data feeds regularly — up to once a day — to ensure that your product information is current for shoppers.