How do you report an undocumented immigrant?

It's not the duty of private citizens to report unlawfully present foreign nationals unless said person(s) has committed a societal crime. Working illegally is a status crime, the employer is the person who should be reported for employing undocumented workers and/or not having done adequate investigation of the person before hiring them. United States Citizenship and Immigration Services http://www.uscis.gov Immigration and Customs Enforcement, http://www.ice.gov