The TN visa is for Mexican and Canadian professionals who want to work in the United States. It is issued for certain occupations only. It is 
similar to the H-1B visa, but it has unique characteristics. The owner of a TN visa may work up to three years with the possibility of a renewal.
In the case of Mexicans:
How to Apply for the TN Visa?
The first step is completing the DS-160 form online, pay the required fees, submit your photos following the correct format instructions (unless the application is made in an American consulate in Mexico, because you do not need to send any pictures there) and request an appointment at a consular office.
You may apply for it at any American consulate in the world, depending on where the person requesting the TN visa lives.
Interview at the American Consulate
Everyone applying for this visa, between the ages of 14 and 79, must go to a consular office to be interviewed.
The documents to be submitted are:
- The Mexican passport valid for at least six months before the end of your stay in the United States.
- A letter from your employer specifying that the position that you were offered needs to be covered by a person who meets the requirements set out in NAFTA. It is important that detailed information on the professional activity performed in the US (period of time, compensation) is included.
Certain types of job do not require the letter to be accompanied by evidence that the applicant has the necessary professional license to work in the US since such certifications can be acquired afterwards. However, if the applicant has them, it is highly recommended to present them along with the letter.
Relatives of the Applicant
The spouse and children (under 21 and unmarried) can apply for a TD visa to accompany the holder of a TN visa to the United States.
It is not necessary that the relatives are Mexican. Keep in mind that although they can live and study in the United States, they are not authorized to work.
Period of Validity of the TN Visa for Mexicans
Generally, visas are valid for up to three years. However, there is always the option to extend their period of validity.