H-1B and H-1B1 "continuation of previously approved employment" filed ONLY at NSC

Starting September 1, 2016, only the Nebraska Service Center (NSC) will accept Form I-129 H-1B and H-1B1 petitions in which the petitioner requests a "continuation of previously approved employment without change from the same employer" in response to Question 2, and asks USCIS to "notify the office in Part 4," "extend the stay of the beneficiary," or "extend the status ... based on a free trade agreement" in response to Question 4. USCIS may reject any misfiled petitions or applications after August 31, 2016.

https://www.uscis.gov/news/alerts/nebraska-service-center-accept-certain-h-1b-petitions