Under what circumstances must a free writing prospectus be filed with the SEC?

Why B — An issuer FWP must be filed on the date of first use; an underwriter FWP must be filed only if it contains material information not included in the registration statement

Under Rule 433, an issuer's free writing prospectus must be filed with the SEC on the date of first use. For underwriter FWPs, filing is required only if the FWP contains information that represents a material modification or supplement to the information in the registration statement. FWPs that consist solely of a description of the terms of the offering or the securities do not need to be filed if they are prepared by the underwriter. All FWPs must include a specified legend advising investors to read the statutory prospectus and providing information on how to obtain it.