Question: Do you recommend filing for an extension of my TN visa status at the border or by mail with USCIS?
Reply: When deciding whether to renew at the border or a preflight inspection, or by mail through USCIS, you should consider several factors such as travel needs, proof of employment authorization, requirements, personal preferences, and cost .
For example, if your I-94 expires in one month, then you may want to consider filing at the border or airport. Filing through USCIS is still an option, but could lead to complications if processing time is slow and you need to travel outside the U.S. Under the 240 Day Rule, while your TN extension petition is pending with USCIS you will have authorization to continue working for the same employer for 240 days after your I-94 expires. But once your I-94 expires, you cannot depart the U.S. and re-enter as a TN worker until USCIS has approved your extension petition, or you obtain a new TN at the border or airport.
Also, many employers are unaware of the 240 Day Rule, and may question whether you still have employment authorization during this period. Another issue involves the upcoming I-9 Employment Eligibility Verification rules, which appear to conflict with the 240 Day Rule. The new I-9 rules will require an employer to re-verify any employee with expiring employment authorization beginning on April 3, 2009. These rules require that all documents presented during the verification process must be unexpired, and do not specifically provide for the documentation of employment authorization based on the 240 Day Rule.
On the other hand, filing an extension of TN status through USCIS has the advantage of avoiding a face-to-face interview with an immigration inspector, which some individuals find stressful and intimidating. USCIS does not adjudicate TN applications at the border or airport. USCBP, a separate bureau of the Department of Homeland Security, reviews TN cases at the border / airport. CBP inspectors, who are responsible for securing America’s borders, tend to take a more enforcement oriented and narrow interpretation approach to TN visa applications. A denial at the border may result in a refusal of admission to the U.S. Whereas USCIS may issue a Request for Further Evidence before an outright denial, which will allow you time to address any shortcomings of the petition.
You should also compare travel costs vs. USCIS filing fees. The USCIS filing fee for an I-129 TN petition is $320. The filing fee for an I-539 is $300. The filing fee for a TN at the border is $56; for a TD $6. The filing fee for a TN at the airport is $50.
Read more about filing for a TN at the border vs. USCIS.