Concurrent TN status is allowed, but you can only have 1 physical TN visa. For concurrent employment your existing visa would have to be cancelled and a new visa listing both employers issued. Thus, you would be giving a consular officer the opportunity to cancel your visa. Thus, depending upon the facts of your case, it may be better to file with USCIS. Consult with an experienced immigration attorney for case specific advice.
While this answer is provided by a Florida Bar Certified Expert in Immigration and Nationality Law, it is for general information purposes only and an attorney/client relationship is neither intended nor created. You should seek out qualified counsel to review your case and provide you with advice specific to your situation. Call +1-561-478-5353 to schedule a consultation with Mr. Devore.
TN's can be filed in the U.S. with USCIS as of October of 2012. Review form I-129 and the filing instructions. You may also want to consider an H-1B for the fall with either or both of your companies if you are contemplating immigrating.
For a TN visa you can apply within the United States with form I-129. But you should consult with an immigration attorney to ensure your proposed course of action wont have negative consequences.
I agree with my colleagues. However, you owe it to yourself to contact a lawyer, whether myself or one of my colleagues. A lawyer will work with you to ensure that all of your options have been explored and you are committed to the best course of action. If you appreciate the time spent preparing this answer, kindly consider marking it BEST ANSWER or HELPFUL. Also, please be sure to read my disclaimer below. Good luck to you.
Dean P. Murray
The Murray Law Firm
560 Sylvan Avenue
Englewood Cliffs, NJ 07632
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