my typo, employee letter should be employer letter which is your offer letter and shows your salary, title and full-time exployee or temp, e.g., 1year. attorney letter is the letter from company's immigration attorney, which states that according to NAFTA, you are eligible for TN status, blah blah. it's kind of bond, when your TN expired, you need to let the attorney know. my personal experience is that the attorney letter is the most important, if the company giving you the offer has immigration attorney, they will know how to take care of it.