The SEC has indicated on its website that, in the event of a federal government shutdown because of “a lapse in appropriations” on October 1, the SEC will remain “open and operational.” Any changes after October 1 will be announced on the SEC’s website. The SEC’s current plan in the event of atotal SEC shutdown is posted  here.  (It does not address the type of partial shutdown that  occurs if the SEC still has some funds available, but not enough to maintain full operations over a full quarter, as happened in 2013.)