This Practice Note reviews the subsections of Rule 424 under the Securities Act of 1933, and the related Rules 430A and 430B, to help counsel determine which Rule 424 subsection they should file a prospectus or prospectus supplement under in an SEC-registered securities offering. This Note examines Rule 424 filings in IPOs and in shelf offerings, including registered medium-term note (MTN) programs. It also offers guidance on several common issues that can arise in the context of filings under Rule 424.