It is limited to certain professions stipulated under NAFTA.
TN status is granted in one year intervals and must be renewed on an annual basis.
There is no limit to the number of years an individual may hold TN status, but the employment must be temporary in nature.
TN visa classification is not to be used for tenured or tenure-track faculty or for permanent staff positions.
Like the H-1B, the TN visa is employer and position specific.