The Immigration and Nationality Act (INA) prohibits the entry of certain employment-based immigrants unless the Department of Labor (DOL) has certified that there is a shortage of U.S. workers to perform such labor and that the employment of the alien will not adversely affect wages and working conditions for U.S. workers. The purpose of this provision, known as labor certification, is to safeguard U.S. workers. The labor certification requirement applies only to the second and third employment-based preferences. Labor certification is not required for immigrants who are priority workers, immediate relatives of U.S. citizens, special immigrants, or who are entitled to visa preferences because of family relationships or because they are refugees.

Immigrants coming to perform labor must obtain a labor certification if they are to be employed by U.S. or foreign firms conducting business in the United States. The procurement of a labor certification is usually the first of three steps required to obtain permanent resident status by immigrants in the second and third employment-based preference categories. Employment is defined as ''permanent full-time work by an employee for an employer other than oneself.''  An investor is not regarded as an employee for this purpose. The statute defines ''employer'' as a ''person, association, firm, or corporation which currently has a location in the United States to which U.S. workers may be referred for employment, and which proposes to employ a full-time worker at a place within the United States or the authorized representative of such a person, association, firm or corporation.'' An alien who claims exemption from the labor certification requirement has the burden of proving entitlement to such exemption.

As of March 28, 2005, the procedure for obtaining labor certification has been completely overhauled by the PERM regulations.  These regulations set up an attestation and audit system that requires the employer to obtain a prevailing wage determination for the position, perform pre-filing recruitment for the position and then file the PERM application through an online system 30-180 days after the completion of all recruitment.  The system has different standards of recruitment based on whether the position is a skilled position or a professional one.  Schedule B, which listed unskilled occupations ineligible for labor certification, has been eliminated.  Unskilled occupations may now be certified based on the results of the labor market test.

Schedule A Occupations

The DOL has long maintained a schedule of occupations in its regulations for which the individual labor certification procedure need not be followed; those occupations are considered precertified. Based on an occupation's inclusion on that schedule, the employer may file permanent  residence papers directly with the USCIS without first going to the DOL for a labor certification. Included among the papers filed with the USCIS is the labor certification application form, ETA Form 9089, an SWA prevailing wage determination, and evidence that notice of the application has been given to a bargaining representative (if applicable) or to employees.

Group I of Schedule A includes physical therapists and professional nurses. Group II of Schedule A includes aliens of exceptional ability in the sciences or arts (excluding the performing arts), including college and university teachers of exceptional ability who have been practicing their science or art during the year prior to application and who intend to practice the same science or art in the United States. For purposes of this Group II, the term ''science or art'' means any field of knowledge and/or skill with respect to which colleges and universities commonly offer specialized courses leading to a degree in the knowledge and/or skill.