13F filings: what institutional holdings reports show and miss

Every quarter, thousands of investment managers tell the Securities and Exchange Commission (SEC) which US-listed stocks they owned at the end of the quarter. Those reports, filed on Form 13F, are the raw material behind every "top holders" table and every headline about what a famous fund bought or sold. They are public, free and searchable on EDGAR.

They are also old by the time you see them, partial by design and easy to over-read. A 13F shows a snapshot of long positions in a defined list of securities as of the last day of a quarter, published up to 45 days later. It leaves out short positions, cash, most foreign shares and everything that happened since. This guide explains who files, what is in and out, how a 13F differs from the 5% ownership reports on Schedules 13D and 13G, and how to use the data without being fooled by it, with Berkshire Hathaway's reported Apple position as the worked example.

Who has to file a 13F

Section 13(f) of the Securities Exchange Act of 1934 and Rule 13f-1 apply to an institutional investment manager: any entity that exercises investment discretion over other people's money, or its own, in securities. That covers mutual fund companies, hedge funds, pension funds, banks, insurers, broker-dealers and endowments.

The trigger is size. A manager files if the securities it manages that appear on the 13F List had an aggregate fair market value of at least $100 million on the last trading day of any month of a calendar year. Once that happens, it files for the quarter ending December 31 of that year and for each of the first three quarters of the next year. The $100 million line is a fixed dollar amount in the rule, not indexed to inflation or market growth, so the filer population includes many mid-sized managers, not only giants.

Where two managers share discretion over the same securities, only one of them reports them, and the other names it on its cover page. That is why a parent company may file one 13F covering several subsidiaries, and why the same holding never appears twice.

The 45-day clock

The report is due within 45 days after the quarter ends. If the 45th day falls on a weekend or holiday, the deadline moves to the next business day. The SEC's own FAQ gives the example of the fourth quarter of 2025: the deadline of Saturday, February 14, 2026 moved to Tuesday, February 17, 2026, after the Presidents Day holiday.

Most large managers file close to the deadline, so the newest data for a stock usually appears in a cluster in the middle of February, May, August and November.

What a 13F contains, and what it leaves out

A 13F has a cover page, a summary page (number of entries and total value) and an information table: one row per holding, with the issuer, the class, the CUSIP, the value, the number of shares, whether the manager has sole, shared or no voting authority, and the investment discretion. Options appear as separate rows in terms of the underlying shares, marked PUT or CALL.

The 13F List is the controlling document. The SEC publishes it every quarter, and managers may rely on it to decide what to report. If a security isn't on it, it doesn't belong on a 13F.

Managers may also ask the SEC for confidential treatment of a position, for example while they are still building it, and file it later. Berkshire Hathaway's 13F-HR/A filed August 14, 2025 is a real case: an amendment to its March 31, 2025 report adding positions in D.R. Horton, Lennar and Nucor, with "Confidential Treatment Expired" as the stated reason. For three months, the original March report had been incomplete by design.

A worked example: Berkshire Hathaway and Apple

Berkshire's 13Fs report its Apple stake across several rows, one for each of its reporting subsidiaries and accounts. Adding the rows gives the total:

How 13F differs from Schedules 13D and 13G

A 13F reports a manager's whole long book above a size threshold. Schedules 13D and 13G report a stake in one company once the holder beneficially owns more than 5% of a class of its voting equity. The SEC tightened their deadlines in amendments adopted October 10, 2023:

The revised Schedule 13G deadlines applied from September 30, 2024. A 13D is the one to watch for activism: it states the holder's purpose and plans, and a new one often marks the start of a campaign. A 13F says nothing about intent.

How to use 13F data, and its traps

Good uses. Seeing which kinds of investors own a stock (index funds, active managers, hedge funds); tracking how concentrated ownership is; following a long-term manager's largest positions over years; checking whether a stock's institutional base is growing or shrinking.

Traps:

• Staleness. By the time you read it, the manager may have sold everything. Treat a 13F as history, not as a live portfolio.
• Partial picture. No shorts, no cash, no non-US shares and no bonds. A fund that is long a stock and short a competitor shows only the long side. A position that looks huge may be hedged.
• Options distort. A large CALL row is exposure to the underlying shares, not shares owned, and the 13F doesn't give strike prices or expiry dates.
• Mirroring is risky. Copying a manager's 13F means buying positions it chose months ago, at different prices, without knowing whether it still holds them or why it bought.
• Index funds dominate. The biggest holders of most large US companies are index managers that hold the stock because it is in the index. Their stakes say little about the company.
• Confidential treatment and amendments. A position may be missing now and appear in a 13F-HR/A later, as Berkshire's 2025 amendment showed.

13F and its neighbours

See Insider trading filings: Forms 3, 4 and 5 and how to read them for Form 4 and Form 8-K: what triggers it, the item numbers and how to read one for company events.

How Finabase does it

A company's Holders tab starts with Ownership: shares held by insiders, by institutions, float held by institutions and the number of institutions. For Apple on October 30, 2026 it showed 66.34% held by institutions across 7,715 institutions.

Below that, Top institutional holders and Top mutual fund holders list each holder's percentage held, shares, value and a Reported date. The institutional rows come from 13F data. Apple's top rows on October 30, 2026 all carried a Reported date of June 29, 2026, meaning the June-quarter snapshot filed by mid-August, not trades from June 29 itself. Two details to read correctly:

• Value is shares × the current price. BlackRock's 1,162,996,939 shares showed a value of $405.78 billion, which is the share count × $348.91, Apple's close on October 29, 2026, not the June 30 value in the 13F.
• Mutual fund rows carry their own dates (some August or September 2026), because they come from the funds' own portfolio reports, which run on different schedules from 13F.

The Holders tab also has an Insiders table, linking to the market-wide Insider trading page, which is fed by Form 4 rather than 13F.

Frequently asked questions

Who has to file Form 13F?

Any institutional investment manager that exercises investment discretion over at least $100 million of securities on the SEC's 13F List, measured on the last trading day of any month in a calendar year.

How delayed is 13F data?

A 13F is due within 45 days after the quarter ends, so it is at least 45 days old when filed and can be about four and a half months old just before the next one arrives.

Do 13F filings show short positions?

No. The SEC's staff FAQ says short positions should not be included, and long positions are not reduced by shorts in the same issuer. Cash and most non-US shares are left out too.

What is the difference between a 13F and a 13D?

A 13F is a quarterly list of a manager's long holdings in 13(f) securities. A Schedule 13D is a filing about a single company, required within five business days of owning more than 5% of its voting shares with possible control intent, and it states the holder's purpose.

Summary

Form 13F is a quarterly snapshot of large managers' long positions in US-listed securities, filed by every manager with $100 million or more in 13(f) securities within 45 days after the quarter ends. It is useful for seeing who owns a company and how ownership shifts, as Berkshire Hathaway's 14.9% cut to its Apple stake in the September 2025 quarter showed, but it is stale, excludes shorts, cash and most foreign shares, and can be held back by confidential treatment. For single-company stakes above 5%, Schedules 13D and 13G are faster and say more about intent. Read 13F data as history, check its date, and don't mistake it for a manager's current portfolio.