Google announced a significant round of changes for merchants using Google Product Search. These changes only affect Google Product Search listings and not Google Commerce Search or Adwords listings.
For feeds targeting the United States, tax information will be required for all feeds starting June 6th, 2011.
According to Google, product listings that do not include tax information at the account level, or in the “tax” attribute, may be rejected. Google is also recommending the addition of two new attributes - "sale price" and "sale price effective date" (not required) for feeds targeting the U.S. exclusively.
In addition, feeds targeting the U.S., U.K., France and Germany, Google will require unique product identifiers (starting May 3rd, 2011) for all products except apparel and one-of-a-kind items, and shipping information (starting June 6th, 2011).
Feeds from accounts that do not include this inforamtion may be disapproved by Google. Products without unique product identifiers may not be listed in Google Product Search, though the feed may not be disapproved.