Schedule 13D vs 13G: how 5% shareholders disclose their stakes

Any investor whose beneficial ownership of a U.S. public company's registered equity crosses 5% must tell the market, and the choice of form says something about the holder. A Schedule 13D says "I may seek to influence this company"; a Schedule 13G says "I'm just holding." There are two forms because the rules treat active and passive holders differently.

Where the 5% threshold comes from

The obligation is Section 13(d) of the Securities Exchange Act of 1934 and the rules under it (Regulation 13D-G). It bites on beneficial ownership, not on shares held outright: a person beneficially owns a security if they have or share the power to vote it or the power to dispose of it, and options or other rights exercisable within 60 days count toward the total. Two consequences catch people out. A holder can cross 5% without buying anything, because the company retired stock and shrank the denominator. And members of a group acting together are aggregated and treated as one beneficial owner, which is how a coordinated stake becomes reportable even though no single member crossed the line.

The SEC's staff maintains a long set of interpretations on Sections 13(d) and 13(g) for the edge cases, and it is the first place to look when a situation does not fit the summary above.