Who can use it
TN status comes from the U.S.-Mexico-Canada Agreement and is open to citizens of Canada and Mexico, not to permanent residents of those countries. The job has to fall within a listed profession, and you need the credentials that the listing calls for, usually a degree or a recognized license. Self-employment does not fit; a U.S. employer or a foreign employer contracting with a U.S. client generally has to be behind the offer. Canadians commonly apply at a port of entry or preclearance, while Mexican citizens generally need a visa from a consulate first. Spouses and children can accompany you, but a TD dependent cannot work.
The employer letter does a lot of work
The officer usually decides largely from the support letter and your credentials, so the letter needs to describe the job in terms that match the listed profession and the duties you will actually perform. A title that sounds right but duties that look like a different occupation is a common source of refusals. Some listed professions call for a particular degree or license, and the listing's own wording matters more than how the employer usually hires. Bring original diplomas, transcripts, licenses, and, where useful, a credential evaluation. If you have been refused before, keep that record, because it will come up again. Treat every statement at the border as part of your immigration history.
Green card plans and timing
TN status is meant for temporary work, and you should not hold an intent to remain permanently at the time you apply. That creates tension for people whose employers want to start a green card case, and the timing of filings and travel matters a great deal. Some people move to a status that allows dual intent before going further. When we talk, we look at whether your job maps to a listed profession, how your credentials line up, and where you are in any longer-term plan. We explain the trade-offs without telling you how a border officer will decide.
