Several U.S. equity exchanges have filed requests with the SEC to extend trading hours to include a new overnight trading session (commonly referred to as “overnight trading” or “23x5 trading”) effective on Sunday, December 6, 2026. Industry infrastructure, including the Trade Reporting Facilities (TRFs), Securities Information Processors (SIPs) and the National Securities Clearing Corporation (NSCC) have also proposed changes to support 23x5 trading. This CAT Alert addresses the CAT reporting changes that affect Industry Members with respect to 23x5 trading. Specifically, the Industry Member definition of Trade Date has been revised. There will be no changes to existing CAT reporting deadlines for submissions and corrections.