Citizens of Canada and Mexico are often eligible for a U.S. working status for several years, thanks the the North American Free Trade Agreement (NAFTA). This status is limited to professional occupations defined by the treaty, but often employees may be eligible for TN status even if their job is not specifically listed. Citizens of Canada do not require a visa, and can apply for admission in TN status at the border or international airport in Canada. Citizens of Mexico can apply for the TN visa at a U.S. Consulate or Embassy in Mexico.
There are several advantages of TN status over H-1B status: high filing fees charged by the USCIS for H-1B petitions are avoided; processing time is faster; the H-1B quota is avoided; and the employer is not required to pay the "prevailing wage." The disadvantage is that, unlike those in H-1B or L-1 status, the applicant must demonstrate that he or she is in the U.S. only temporarily, and does not intend to immigrate permanently. Often, professional workers will enter the U.S. in TN status (to obtain the advantages noted above), then later change to H-1B status.