What is a 13F filing? A plain-English guide (2026)

A 13F filing is a quarterly report that large US investment managers file with the Securities and Exchange Commission (SEC), listing the US-listed stocks they held at the end of the quarter. It answers one question: what did this manager own, as of that date. It does not say why they held it, what they have done since, or what anyone should do about it.

Who has to file a 13F?

The rule comes from Section 13(f) of the Securities Exchange Act. Any "institutional investment manager" that exercises discretion over at least 100 million US dollars in 13(f)-eligible securities must file. In practice that means most hedge funds, large mutual fund managers, pensions, endowments, and sizeable family offices. The specific form is the 13F-HR ("holdings report").

What a 13F shows, and what it hides

A 13F is useful precisely because it is a primary source: the numbers come from the manager, filed under regulatory obligation. But it is a narrow, delayed window, and reading it well means knowing its edges.

What it includes:

• Long positions in US-listed equities
• Certain call and put options, and convertible notes
• The share count and market value as of quarter-end
• The CUSIP identifying each security, and since 3 January 2023 an optional FIGI alongside it

What it leaves out:

• Short positions (never disclosed on a 13F)
• Cash, most bonds, and non-US-listed holdings
• Any change made after the quarter-end date
• The manager's reasoning or intent

The 45-day lag: the caveat that matters most

Two lags stack up. First, the filing reports holdings as of the quarter-end date. Second, the manager has up to 45 days after that date to file. So on the day a 13F becomes public, the positions it lists can already be six weeks or more out of date, and the manager may have added to or exited any of them. A 13F tells you what was held on a specific past date. It is not a live portfolio.

This is why every holding on Flock carries its filing date and a freshness stamp. The same disclosure, sourced and dated, looks like this:

Filed 2026-05-15·SEC 13F·view source

How to read a 13F without over-reading it

Treat a 13F as a dated snapshot, not a to-do list. A few practical points:

• Compare quarter over quarter to see what changed, rather than reading a single filing in isolation.
• Check the filing date before assuming a position is current. The 45-day lag is real.
• Cross-reference across filers: when several independent managers disclose the same name across their filings, that overlap is a matter of public record you can verify yourself.
• Follow the source link to the original EDGAR filing for anything you plan to rely on.
• Watch the units in older filings. Values have been rounded to the nearest dollar only since 3 January 2023; before that the same column was rounded to the nearest thousand dollars. See the 13F Information Table for the full column set.

Flock decodes 13F-HR filings into readable holdings, keeps each one stamped with its filing date and a link back to SEC EDGAR, and lets you track filers over time. What the data means for you is your call to make.