Final answer:
A registration statement filed with the SEC is effective when it is approved by the SEC. The effectiveness duration varies depending on the type of offering.
Step-by-step explanation:
A registration statement filed with the U.S. Securities and Exchange Commission (SEC) becomes effective when it is approved by the SEC. The effectiveness of a registration statement depends on the type of offering being registered. For example, in the case of an initial public offering (IPO), the registration statement is effective for a period of at least 20 days before the securities can be offered to the public. During this time, potential investors have the opportunity to review the information provided in the registration statement and make informed investment decisions.