Businesses, like individuals, must file taxes with the federal government and their respective state governments. In Wisconsin, businesses need a tax identification number to file taxes with the Wisconsin Department of Revenue. You can find a business’ tax identification number through the Department of Revenue website.
Choose whether you want to look up filings for withholding or sales tax. If the business is a sole proprietorship, choose the option to search by Social Security number. Otherwise, choose to search by the business’ federal employee identification number. Enter whatever ID number you chose, as well as the business’ name or sole proprietor’s last name and zip code. If you get a “no information available” message, either the information entered was incorrect or no tax data exist for that company.