Form 4 is split into two tables because insiders hold two different kinds of instruments. Table I covers non-derivative securities, mainly common stock held or traded outright. Table II covers derivative securities, instruments whose value is derived from the underlying stock. Mixing the two tables up is the source of the most dramatic misreadings of insider filings, including headlines that turn a routine option grant into an apparent buying spree.
A non-derivative security is the thing itself. Common stock, and in some cases preferred stock or units with a fixed claim, sits in Table I. When an insider buys 5,000 shares on the open market, that line appears in Table I with the price paid and the new total owned. Purchases and sales that traders follow, codes P and S, are Table I events for the stock itself. If you only have time to read one table, Table I is where actual share ownership changes hands.
A derivative security gives the holder a right or obligation tied to the underlying stock without being the stock. Employee stock options are the most common example on Form 4, alongside restricted stock units in some presentations, warrants, convertible notes, and convertible preferred stock. Table II records the terms that define the instrument: the exercise or conversion price, the number of underlying shares it relates to, the transaction date, and the expiration date. Those terms, not a market price for stock, are what a Table II line is really reporting.
When a company grants options, Table II shows an acquisition, code A, of a derivative covering a stated number of shares. It can look, at a glance, like the insider acquired that many shares. They did not. They received a right to buy shares later at the exercise price, usually granted as compensation, often vesting over years, and worthless if the stock falls below the exercise price before expiration. No personal money was spent and no shares changed hands. The same logic applies to other awards: a grant is pay being delivered in a form linked to the stock, not an insider choosing to invest at a market price.
The tables connect when a derivative is exercised or converted. Suppose an officer exercises options for 10,000 shares. Table II shows the derivative being disposed of, code M, and Table I shows 10,000 shares being acquired, also code M, at the exercise price. Readers who only scan Table I may see a large acquisition and miss that it came from an option granted years earlier, sometimes with a same day sale, code S, or tax withholding, code F, right beside it. The full sequence, grant, exercise, and any sale, is the real story, and it is usually compensation lifecycle rather than fresh buying.
That said, derivatives are not irrelevant. An insider who exercises options early and holds the shares, rather than selling immediately, increases real share exposure with real money paid for the exercise and taxes. An insider buying call options in the open market would be unusual and would appear in Table II as a purchase. The point is not to ignore Table II, but to translate it correctly: rights and obligations first, shares only when an exercise or conversion actually happens.
Understanding the two tables prevents the most common Form 4 errors. This explanation is for education only and should not be taken as investment advice.