On occasion, the securities markets may unexpectedly close for business, for example, on a national day of mourning declared by the president of the United States. This Notice provides updated guidance to members regarding SEA Rules 15c3-1, 15c3-3, 17a-5, Rule 204 under Regulation SHO, FINRA Rules 4210, 4230(b), 4521 and 4524, and Federal Reserve Board Regulation T in the event of such an unexpected close.