The thing that took me a while to understand about insider buying is that the person doing it is not playing the same game you are, and not because they know something you don't. They might, but that is not the interesting part. The interesting part is that they are trading under a legal constraint you are not, and that constraint quietly shapes the timeframe of everything they do in their own stock. Once I started reading insider buys with that constraint in mind, a lot of them stopped looking like noise.
What Section 16(b) actually does
Section 16 of the Securities Exchange Act covers company insiders, which for this purpose means officers, directors, and anyone who owns more than ten percent of a class of the company's equity. Section 16(a) is the part that makes them file their trades, so you can see them at all. Section 16(b) is the part that most people skip over, and it is the one that matters here.
The rule is short swing profit disgorgement. If an insider buys and sells, or sells and buys, the same company's stock within a six month window, any profit that can be matched between those trades belongs to the company. Not a fine, not a penalty in the usual sense. The insider simply does not get to keep the gain. The company can sue to recover it, and in practice shareholders and their lawyers are the ones who go looking, because there is a fee in it for them. It is close to strict liability. It does not matter whether the insider actually had material nonpublic information. It does not matter if the timing was innocent. If the trades match inside six months and there is a profit, it gets clawed back.
The matching is the part people get wrong. It is not first in first out and it is not average cost. Courts use a rule designed to produce the maximum possible recoverable profit. They pair the lowest priced purchase with the highest priced sale inside any six month window, then the next lowest with the next highest, and so on. You can lose money on paper across a period and still owe disgorgement, because the rule ignores your losing pairs entirely and only counts the profitable matches. That asymmetry is deliberate. It is meant to make the whole exercise so unrewarding that insiders don't bother trying to time short swings at all.
Why this turns a buy into a holding-period signal
Here is where it gets practical. An insider who buys shares on the open market has just started a six month clock. If the stock runs up next month and they want to take the gain, they can't, not without handing every dollar of matched profit back to the company. So the realistic exits for an open market buy are: hold past six months, or sell at a loss. Neither of those is a quick flip.
Which means the buy itself carries information about timeframe that has nothing to do with what the insider thinks the stock is worth next week. When an officer puts real money into their own company's stock on the open market, they are structurally committing to a hold of at least six months, because the alternative is buying high and selling low on purpose, which nobody does. The purchase is a statement that they expect to be comfortable holding through that entire window. That is a different animal from a trader taking a swing they plan to close in ten days.
I want to be careful not to oversell this. It does not tell you the stock goes up. Insiders are wrong all the time, and plenty of them buy into declines that keep declining. What it tells you is the intended timeframe of the person on the other side of the disclosure. And matching your own horizon to theirs is most of the battle in following any smart-money trade, insider or otherwise.
The exceptions that will trip you up
If you start reading Section 16 filings, you will quickly hit trades that look like they should trigger disgorgement and don't. Most of them fall into a few buckets, and knowing them keeps you from misreading the signal.
- Option exercises and grants. A lot of what shows up on Form 4 is not an open market decision at all. Exercising options, receiving restricted stock, and similar compensation events are handled differently, and many are exempt from the matching rule under specific SEC exemptions. These are not conviction buys. Someone exercising vested options and selling to cover taxes is doing paperwork, not making a call.
- 10b5-1 plans. Insiders can set up a pre-arranged trading schedule in advance, then trades execute automatically regardless of what they know later. Sales under these plans are routine and mechanical. A sale is not the same as a bearish view when it was scheduled months ago on a calendar.
- Bona fide gifts and inheritances. Transfers that are not purchases or sales in the market sense generally don't enter the matching at all.
The filing codes on Form 4 tell you which is which. Transaction code P is an open market purchase, and S is an open market sale. Those are the ones where the six month constraint actually bites and where the timeframe signal lives. Code M, A, G, and the rest are the compensation and transfer machinery you mostly want to filter out when you are hunting for conviction.
How I actually use it
My rule of thumb is simple. When I see an open market purchase, a code P, from an officer or director, I treat it as a claim that the buyer is willing to hold for at least six months. So if I decide to ride along, I set my own review date six months out and I stop looking at the position in between. The insider physically cannot flip it inside that window without giving the profit away, so watching for a two week pop and copying their supposed exit is a fantasy. There is no exit to copy. The only exits available to them are the slow ones.
The failure mode I keep seeing people fall into is copying the entry and then panicking on the first drawdown, selling in week three while the insider is legally frozen into the trade. You end up taking the downside of a six month position with the patience of a day trade. If you are going to follow the buy, you have to inherit the constraint that came with it, which means accepting that the person you are copying is not going anywhere for half a year and neither should you.
A short checklist I run before treating an insider buy as a signal worth mirroring:
- Is the transaction code P, an actual open market purchase, and not an option exercise or a grant.
- Is the buyer an officer or director with real skin, rather than a passive ten percent holder rebalancing.
- Is the dollar size meaningful relative to what that person likely earns, so it reads as conviction and not a rounding error.
- Am I prepared to hold for the full six month window, because the person I am copying has effectively already committed to it.
That fourth point is the whole thing. The rule that stops insiders from flipping is also the rule that tells you what horizon to bring. We surface these open market purchases in Blockcircle's disclosure feeds with the transaction codes attached, so you can filter the paperwork out and see the actual P buys, but the mental model matters more than the tool. Read the buy as a six month floor on someone else's patience, and hold yourself to the same floor, or don't follow it at all.