Knowledge of federal regulation is the key to an employer's successful navigation of worksite enforcement under the Immigration and Nationality Act. This article surveys the main worksite enforcement issues that employers face when employing aliens in the US. Major topics of relevance to employers include proper documentation, inspection and audit procedure, and the civil and criminal penalties and the prosecutions associated with them. The employer may not demand specific documents from a new hire, and must accept documents presented which appear genuine and to relate to the employee, It is illegal to discriminate in employment decisions on the basis of national origin. Pursuant to 8 CFR Section 274a2(b)(2)(ii), an employer must receive three (3) days notice before an inspection, which is announced by a served or mailed Notice of Inspection. During this time, employers may collect, review and correct errors in their I-9s.