TN (Treaty NAFTA) status is a special non-immigrant status in the United States unique to citizens of Canada and citizens of Mexico. Beginning in 1988, individuals practising one of the professions identified in the Canada - United States Free Trade Agreement are able to obtain TN status for legal work in the United States and Canada, creating freedom of labor movement. TN status is recognized in the North American Free Trade Agreement (NAFTA) which began in 1994. It allows U.S., Canadian and Mexican citizens the opportunity to work in each other's countries in certain professional occupations. It bears a similarity, in some ways, to the H-1B visa, but also has many unique features. Within the TN set of occupations, an American, Canadian or Mexican can work for up to three years at a time. However, the TN status may be renewed indefinitely in three-year increments, although it is not a 'permanent' visa and if US immigration officials suspect it is being used as a de facto green card, they may elect to deny further renewals. The set of occupations permitted to petition for TN status is also quite a bit more limited than for the H-1B visa. Spouse and dependent children of a TN professional can be admitted into the United States in the TD status.