What a Form 13F does and does not tell you

Who files one, and when

Rule 13f-1 requires an institutional investment manager that has discretion over accounts holding Section 13(f) securities worth at least $100,000,000 on the last trading day of any month of a calendar year to file a report on Form 13F. The form's instructions set the timing: within 45 days after the end of the calendar year and within 45 days after the end of each of the first three quarters. A manager reporting on 30 June has until mid-August.

Which securities count is set by the SEC's official list of Section 13(f) securities, published quarterly. The SEC's Form 13F frequently asked questions say the list mainly includes US exchange-traded stocks, shares of closed-end investment companies and ETFs, plus certain convertible debt, equity options and warrants. Mutual fund shares are not on it.

What a 13F contains

The filing has a cover page and an information table. The table has one row per position, and each row gives the issuer, the class of security, a CUSIP identifier, the value, the number of shares, whether the manager has investment discretion, any other managers it reports with, and the voting authority. Since compliance began in January 2023, values are reported to the nearest dollar, where before they were in thousands, under the SEC's 2022 amendments.

What it leaves out

• Trade dates and prices. A 13F reports what was held on one day. It does not say when a position was bought, at what price, or in what order. Comparing two quarters shows a change between them, and nothing about how it came about.
• Short positions. The SEC's FAQ says short positions are not reported and must not be subtracted from long positions in the same security. Short positions go on a different form, Form SHO, under a rule effective in January 2024 (Release 34-98738), and that is a separate filing.
• Foreign-listed shares. Securities that trade only on non-US exchanges are not reported, according to the same FAQ.
• Small positions. A manager may leave out a position if it holds fewer than 10,000 shares of an issuer and those shares are worth less than $200,000 in total. Both conditions must be met, and the manager may include such positions if it prefers.
• Anything held by managers below the threshold. The duty starts at $100 million of reportable securities.
• Timeliness. Up to 45 days pass between the quarter's end and the deadline, so the snapshot can be a month and a half old on the day it is filed.

A real filing, read row by row

Berkshire Hathaway's Form 13F-HR for the quarter ended 30 June 2026 was filed on 14 August 2026, 45 days after quarter end. Its cover page gives:

• 89 table entries, with a total value of 299,253,556,246 dollars;
• 14 other included managers;
• no confidential-treatment omissions.

The information table has 89 rows, and the values add up to the figure on the cover. Reading it:

• The largest single row is American Express common stock: 149,061,045 shares valued at 50,419,898,471 dollars, reported with other managers 4 and 11.
• Apple appears on 12 separate rows. Added together, they come to 65,950,296,923 dollars. The table has an "other manager" column, and one issuer's shares are split across rows by the manager they are attributed to.
• So the largest row (American Express) and the largest holding by issuer (Apple) are not the same, and a reader who sorts the table by value without adding up rows by issuer sees the wrong picture.

Nothing in the filing says when any of these shares were bought. It says what was held on 30 June.

Three habits that avoid most mistakes

1. Add up the rows of one issuer before ranking holdings.
2. Compare filings from the same manager with a note of the period each covers, and talk about changes between quarter ends, not about trades.
3. Check for amendments. A manager can amend a filing, so the original is not always the final word.

How a 13F differs from a Schedule 13D or 13G

A 13F is periodic and covers a whole portfolio. Schedules 13D and 13G are event-driven and cover one issuer: they are filed when a holder passes 5% of a class. The guide to 13D and 13G explains the deadlines, and the guide to the 13F lists the fields. OQRO tracks a set of 16 funds, which is a small part of all filers, and says so on the pages where the data is shown.