Is Insider Trading Legal? It Depends Which One You Mean

Both answers are correct, because two different things share the name. One is a reporting duty: an officer buys shares in their own company, files a Form 4 within two business days, and the trade becomes public. The other is a fraud doctrine the courts built decision by decision, carrying up to twenty years in prison. Everything we publish comes from the first kind. That is not a loophole we found, it is the design.

The part that catches people out is what the second kind rests on. The rule that prohibits it never uses the phrase.

What makes insider trading illegal?

The prohibition lives in Rule 10b-5, and the whole rule is one sentence (17 CFR 240.10b-5):

It shall be unlawful for any person, directly or indirectly, by the use of any means or instrumentality of interstate commerce, or of the mails or of any facility of any national securities exchange,

(a) To employ any device, scheme, or artifice to defraud,

(b) To make any untrue statement of a material fact or to omit to state a material fact necessary in order to make the statements made, in the light of the circumstances under which they were made, not misleading, or

(c) To engage in any act, practice, or course of business which operates or would operate as a fraud or deceit upon any person,

in connection with the purchase or sale of any security.

One sentence, one full stop, three lettered clauses. Read it again and look for the words insider trading. They are not there. Nor is anything about material nonpublic information, corporate officers, or trading on an advantage. It is a general antifraud rule, adopted in December 1948 and last amended in 1951, and it says nothing at all about the offence everyone uses it to describe.

Congress has used the phrase, but only in headings. One section is titled “Civil penalties for insider trading” (15 U.S.C. 78u-1) and another “Liability to contemporaneous traders for insider trading” (15 U.S.C. 78t-1). Neither operative text uses it. Both describe someone who traded “while in possession of material, nonpublic information”.

A heading is not a definition, and there is no definition. The Congressional Research Service says so without hedging: “legislators have not enacted a statutory definition for the offense. Its elements are instead the product of judicial decisionmaking, with SEC rules supplementing the core prohibition” (CRS IF11966, 2021). Bills to codify one passed the House in December 2019 and again in May 2021. Neither was taken up by the Senate.

So the doctrine came from the courts, and it turns on something narrower than most people assume.

In Chiarella v. United States, decided 18 March 1980, the Supreme Court held that “a duty to disclose under § 10(b) does not arise from the mere possession of nonpublic market information”. Knowing something the market does not know is not the offence. The Court declined to recognise “a general duty between all participants in market transactions to forgo actions based on material, nonpublic information”.

In United States v. O’Hagan, decided 25 June 1997 by six votes to three, the Court accepted the misappropriation theory. In its own words, that theory “holds that a person commits fraud ‘in connection with’ a securities transaction, and thereby violates §10(b) and Rule 10b-5, when he misappropriates confidential information for securities trading purposes, in breach of a duty owed to the source of the information”.

Put those together and the shape is clear. The offence is a breach of duty, not an information advantage. A lawyer who trades on what a client told them has stolen something from the client. An analyst who works out the same conclusion from public filings has stolen nothing from anyone, and is doing the thing the market is supposed to do.

What makes insider trading legal?

The other kind is legal because it is disclosed, on a clock, to everybody at once.

Section 16 applies to a defined group: “Every person who is directly or indirectly the beneficial owner of more than 10 percent of any class of any equity security … or who is a director or an officer of the issuer” (15 U.S.C. 78p). Those people may trade their own company’s stock. What they may not do is keep it quiet. A change in ownership has to be reported “before the end of the second business day following the day on which the subject transaction has been executed”.

Two business days is a hard deadline, and it is mostly met. Take every Form 4 filed in calendar year 2025, all 172,023 of them: 152,319 arrived within two business days of the transaction period the filing itself reports. That is 88.55%. The median filing takes two business days. At the other end, 7,070 took longer than five.

That figure counts corrections too. A Form 4/A filed months later to fix an earlier one lands in the data as a single very late filing, which is true but is not what the deadline is about. Counting original filings only, 151,955 of 169,468 arrived on time, or 89.67%. Our business day count also treats US federal holidays as working days, which stretches every measured gap a little. Both numbers therefore understate how well the deadline is met rather than flattering it.

For comparison, a member of Congress reporting a stock trade gets up to 45 days, and the amount they disclose is a bracket rather than a number. Same country, same year, two very different ideas of prompt.

Disclosure is the price of the trade being allowed. That is the sentence to keep.

What is the six month rule for corporate insiders?

Here is the rule that does the most work and gets the least attention. Section 16(b) says that any profit an insider realises “from any purchase and sale, or any sale and purchase, of any equity security of such issuer … within any period of less than six months … shall inure to and be recoverable by the issuer”.

Three things about that are worth slowing down for.

It does not ask what they knew. There is no mention of information, intent, or advantage anywhere in the subsection. Buy in March, sell in July at a profit, and the profit is recoverable whether or not anything improper happened. Good faith is irrelevant to it.

The money goes to the company, not the government. This is not a fine. The profit belongs to the issuer whose stock was traded.

Any shareholder can enforce it. The statute lets suit be brought “by the issuer, or by the owner of any security of the issuer in the name and in behalf of the issuer if the issuer shall fail or refuse to bring such suit within sixty days after request”. Ask the company to sue, wait sixty days, and if it does nothing you may sue in its name. There is a two year limit from the date the profit was realised.

A rule that needs no proof of wrongdoing and that any single shareholder can enforce shapes behaviour more quietly than the headline offence does. It is also why a Form 4 buy followed by a Form 4 sale a few months later is a thing insiders and their counsel watch closely.

What are the penalties for illegal insider trading?

Civil first. The SEC may seek a penalty that “shall not exceed three times the profit gained or loss avoided as a result of such unlawful purchase, sale, or communication”. For someone who controlled the person who traded, the cap is “the greater of $1,000,000, or three times the amount of the profit gained or loss avoided” (15 U.S.C. 78u-1).

Criminal is separate and needs wilfulness. A natural person faces a fine of up to $5,000,000 and up to 20 years in prison. An entity faces up to $25,000,000 (15 U.S.C. 78ff).

Section 16(b) sits outside both. It is not a penalty at all, it is a claim the company has against its own insider.

How do you tell the two apart?

Four questions, all answerable without knowing anything about the person:

Is there a filing? The legal kind produces a document with a name, a date, a share count and a price. The illegal kind is defined by the absence of one.
Who is on the other side of the duty? Liability under the fraud doctrine runs to shareholders under the classical theory, or to the source of the information under O’Hagan. If nobody was owed anything, the fraud analysis has nowhere to start.
Was the information stolen or worked out? Reaching a conclusion from public filings is the opposite of misappropriation, even when the conclusion is valuable.
Did a purchase and a sale land within six months? That is Section 16(b) territory, and it is answered by two dates rather than by anyone’s state of mind.

This describes the rules, it is not legal advice, and a real case turns on facts no filing shows.

The practical part is that every Form 4 is public the moment it lands, and reading one is a skill rather than a subscription. Ours are indexed per person in the insider directory, our methodology page sets out what we count, and if you want to read a filing properly, start with the transaction code rather than the direction letter.