• First Preference (EB-1 priority workers);
• Second Preference (EB-2 workers with advanced degree and those exceptional ability);
• Third Preference (EB-3 professionals, skilled workers, and other workers);
• Fourth Reference (EB-4 certain special immigrants, including Religious Workers); and
• Fifth Preference (EB-5 employment creation).

Under employment-based immigration categories, in many cases, a labor certificate (L/C) is required before one may file for an immigrant visa application.

Standard Operating Procedures of USCIS for the processing and adjudication of I-140 employment-based immigrant petitions.

11/01/2007: Handbook for Employer - Instructions for Completing the Form I-9.