Certain Canadian and Mexican workers may also apply for TN visas under the North American Free Trade Agreement (NAFTA). Only workers in certain professional fields qualify for this classification. TN visa applicants are typically required to possess some formal post-secondary education and/or sufficient work experience. Canadian nationals may apply for TN classification directly at a port of entry along the border while Mexican nationals who are abroad must apply for TN visas at a U.S. consulate. TN workers may be admitted in the U.S. for up to three years and, subject to certain exceptions, are not limited in how many times they may renew their status. TN visas are a great vehicle to extend U.S. employment authorization for qualified Canadian and Mexican workers.