Filings 101

Most of what the world’s richest people do with public companies shows up first in a filing with the US Securities and Exchange Commission (SEC). Here is what each common form is, when it’s filed, and what it can and can’t tell you, with real examples from the filings we track.

Form 4: insider trades

What it is: A report of a trade by a company insider: a director, an officer, or anyone who owns more than 10% of a company’s shares.
When it’s filed: Within 2 business days of the trade.
What it tells you: Who traded, which shares, how many, at what price, and how many they hold afterwards. A letter code says what kind of trade it was.
What it doesn’t: Why they traded. A sale is often routine, and big holders frequently sell on a pre-set schedule (see 10b5-1 plans below).

Code	Meaning	How to read it
P	Open-market or private purchase	They bought shares with their own money. The clearest signal.
S	Open-market or private sale	They sold. Often routine (taxes, diversification, a pre-set plan).
A	Grant or award from the company	Pay, not a purchase. Common for directors and executives.
M	Option exercise or conversion	Turned options or units into shares. Often paired with a sale.
G	Gift	Shares given away, often to a family trust or charity. No money changes hands.
F	Shares withheld to pay tax or the exercise price	The company kept some shares to cover a bill. Not a market sale.

From our data Charles Koch & family · filed by Koch, Inc. · filed Sep 24, 2026 · Issuer: ASPEN AEROGELS INC · Sold 12.3M ASPN · ~$58.1M · Read the filing on EDGAR ↗

Form 144: planned sales

What it is: A notice that an insider or other “affiliate” plans to sell restricted or control shares.
When it’s filed: On or before the day the sale order is placed, when the planned sales in a 3-month period are over 5,000 shares or $50,000.
What it tells you: That a sale is coming, roughly how many shares, and through which broker.
What it doesn’t: That the sale happened. The trade itself shows up later on a Form 4, and the planned amount can differ from what is actually sold.

From our data Mark Zuckerberg · filed by Zuckerberg Mark · filed Sep 24, 2026 · Read the filing on EDGAR ↗

10b5-1 plans: pre-set trading schedules

What it is: A written plan, set up in advance, that trades shares automatically on a schedule or at set prices. It lets insiders sell (or buy) even when they later learn private news.
When it’s filed: The plan itself is not filed with the SEC. Trades made under it are reported on Form 4, which has a box to mark trades made under a plan. Directors and officers must wait a cooling-off period before the first trade under a new plan.
What it tells you: That a trade was decided months earlier, so it says less about what the insider thinks today.
What it doesn’t: The plan’s full terms, or whether the plan was changed or cancelled before a trade.

From our data Our filing data does not yet record the 10b5-1 box, so we can’t point to an example here.

Schedule 13D vs 13G: big stakes

What it is: Reports filed by anyone who owns more than 5% of a class of a public company’s voting shares. 13D is for owners who may try to influence or control the company (activists, acquirers). 13G is a shorter form for passive owners, like index funds or founders who are not seeking change.
When it’s filed: 13D within 5 business days of crossing 5%, with amendments for material changes. 13G deadlines are longer and depend on the type of owner.
What it tells you: The size of the stake, and for a 13D the owner’s stated plans, such as pushing for board seats or a sale.
What it doesn’t: Day-to-day trading. Between amendments, the stake can change without a new filing.

From our data Changpeng Zhao · filed by YZILabs Management Ltd. · filed Sep 21, 2026 · Read the filing on EDGAR ↗

From our data Israel Englander · filed by MILLENNIUM MANAGEMENT LLC · filed Sep 23, 2026 · Read the filing on EDGAR ↗

Form 13F: quarterly fund holdings

What it is: A list of US-listed stocks and some other securities held by an investment manager that oversees $100 million or more in them.
When it’s filed: Every quarter, within 45 days after the quarter ends. So the snapshot is already up to 45 days old when it is filed.
What it tells you: What a fund (for example a billionaire’s family office or hedge fund) held at the end of the quarter, and by comparison with the last one, what it bought or sold.
What it doesn’t: Short positions, most non-US holdings, cash, or anything traded since the quarter ended. It is a snapshot, not a live portfolio.

From our data Ken Griffin · filed by CITADEL ADVISORS LLC · filed Sep 2, 2026 · Read the filing on EDGAR ↗

8-K: company events

What it is: A company’s report of a major event: a merger, a CEO change, a big contract, results, a bankruptcy.
When it’s filed: Usually within 4 business days of the event.
What it tells you: That something important happened, in the company’s own words, often with the press release or agreement attached.
What it doesn’t: Analysis. The company decides how to describe the event.

From our data Warren Buffett · filed by BERKSHIRE HATHAWAY INC · filed Aug 11, 2026 · Read the filing on EDGAR ↗

S-1: going public

What it is: The registration statement a company files to sell shares to the public for the first time (an IPO).
When it’s filed: Before the IPO, often with several amendments (S-1/A) as the deal takes shape.
What it tells you: The company’s business, finances, risks, and who owns what before the listing, including founders’ and big investors’ stakes.
What it doesn’t: The final price or whether the IPO will happen. Those come later.

From our data No S-1 filings among the filings we track from the last 90 days.

Form D: private raises

What it is: A short notice that a company or fund sold securities privately, without a public offering.
When it’s filed: Within 15 days after the first sale in the offering.
What it tells you: That a raise happened, roughly how much was offered and sold, and some of the people running the issuer.
What it doesn’t: Who invested or at what valuation.

From our data No Form D notices among the filings we track from the last 90 days.

Find filings yourself

Every filing is public on EDGAR, the SEC’s filing system. Search by person, company or form type with EDGAR full-text search ↗. Our person pages list each tracked person’s filings from the last 90 days, and our company pages show insider trades by the billionaires who hold each company.

This guide explains filings in general terms. It is for information only and is not legal or financial advice.