Which form is filed by institutional investment managers that exercise discretion over $100 million or more in equity securities?

The form that institutional investment managers must file when they exercise discretion over $100 million or more in equity securities is the Form 13F. This filing requirement stems from the Securities Exchange Act of 1934, specifically Section 13(f), which mandates that institutional investment managers disclose their equity holdings if they manage $100 million or more in assets.

Form 13F provides transparency to regulators and the public about the investments held by large institutional investors, giving insight into market trends and investment strategies. The information on this form includes details about the securities owned, including the number of shares and the value of those holdings.

The other forms mentioned serve different purposes. For instance, Form 10-K is an annual report that publicly traded companies must file, providing a comprehensive overview of their financial performance. Form D is used for filing a notice of exempt offering of securities, while Form ADV is related to the registration of investment advisors and includes information about their business practices and fees, not specifically about equity holdings. Therefore, without question, the correct form for institutional investment managers with significant discretionary equity investments is Form 13F.