What Is a 13F Filing?

You've probably seen a headline like "Berkshire Hathaway just disclosed a new $2 billion stake" or "Michael Burry's fund dumped its Nvidia position." Every one of those stories comes from the same underlying document: a Form 13F, filed quarterly with the U.S. Securities and Exchange Commission (SEC).

If you've ever wondered how anyone knows what a hedge fund or mutual fund is holding, this is the answer. This guide walks through what a 13F filing actually is, who has to file one, what it tells you, what it deliberately leaves out, and how to actually use one instead of just reading headlines about it.

The short version

A 13F is a quarterly report that discloses the U.S. equity holdings of large institutional investment managers. It's public, it's free to read on SEC EDGAR, and it's the raw data behind almost every "what are the smart money doing" article you've ever read.

Who has to file a 13F?

Any institutional investment manager -- hedge funds, mutual funds, pension funds, insurance companies, even large family offices -- that manages over $100 million in what the SEC calls "Section 13(f) securities" has to file.

A few details that trip people up:

• The $100 million threshold is measured against a specific list of securities (mostly U.S. exchange-listed stocks, some convertible bonds, and equity options), not the manager's total assets under management. A fund could manage $500 million overall but still be under the 13F threshold if most of that is in bonds, cash, or non-U.S. securities.
• The threshold is checked on the last trading day of any month during the year -- not just at year-end. Cross it once, and you're on the hook for four consecutive quarterly filings, even if your holdings drop back below $100 million the next month. There's no walking it back mid-year.
• Filing deadline is 45 calendar days after the end of each quarter (so Q1 filings are due mid-May, Q2 in mid-August, and so on). The SEC does not grant extensions.

What a 13F actually discloses

For each qualifying security, the filing lists:

• The name of the company and its CUSIP (a unique security identifier)
• The number of shares (or principal amount, for convertible bonds) held
• The market value of that position as of quarter-end
• Whether the manager has sole or shared voting/investment discretion over it

That's it. No commentary, no strategy explanation, no cost basis. It's a structured table of positions, nothing more.

What a 13F does not tell you

This is the part that trips up a lot of first-time readers, and it's honestly more important than what the filing does show:

1. No short positions. A 13F only reports long equity holdings. If a fund is short a stock -- betting against it -- you will never see that on a 13F. This means a fund's public 13F can look bullish on a name it's actually net-negative on overall.
2. No real-time data. Because of the 45-day filing window, by the time you read a 13F the positions inside it could be up to three and a half months out of date. A fund could have completely exited a position the day after the filing's snapshot date, and you wouldn't know for another quarter.
3. No non-U.S. holdings, most bonds, cash, or derivatives beyond basic options. A fund's international stock positions, corporate bond holdings, and cash reserves are all invisible here. A 13F is a partial picture of one slice of a portfolio, not the whole thing.
4. Confidential treatment requests. In some cases a manager can ask the SEC for temporary confidential treatment on a specific position (usually while still building it), delaying disclosure. It's uncommon, but it means "nothing in the 13F" doesn't always mean "no position."

Why 13F filings became a retail-investor obsession

13F data has existed since the 1970s, but it exploded in popularity as a retail research tool once EDGAR made every filing free and searchable online. The appeal is obvious: it's a legitimate, verifiable look at what some of the most sophisticated investors in the world are doing with real capital, updated every three months, for free.

The catch is that most people either don't know the filing exists, or they know it exists but have no easy way to track it across thousands of managers and tens of thousands of tickers every quarter -- which is exactly the gap a site like AlphaSMO exists to close.

How to actually use 13F data (instead of just reading about it)

Knowing the mechanics is one thing; using it well is another. A few practical starting points:

• Follow specific institutions you trust or find interesting. Browse AlphaSMO's institution database or the curated Guru Portfolios list to see exactly what a given fund's current disclosed holdings look like, and how they've changed quarter over quarter.
• Watch for convergence, not single data points. One fund buying a stock is a data point. Several unrelated institutional managers and company insiders buying the same name in the same window is a much stronger signal -- that's exactly what our Smart Money page is built to surface.
• Look at the trend, not the snapshot. A single quarter's holdings tell you less than the direction of change. Our Buy/Sell Trends view is built around exactly this -- which positions are being built up or trimmed across the institutional universe, not just what's currently held.
• Sanity-check the lag. Always note the quarter a filing covers, and remember that anything could have changed since. Treat 13F data as "what this fund was doing three-ish months ago," not "what this fund is doing right now."

A quick worked example

Say you open a fund's most recent 13F filing and see a new line item: 5,000,000 shares of a company, market value $450,000,000, sole investment discretion. Here's how to read that correctly:

• This is a position as of the filing's quarter-end date -- it may have been bought all at once, or built up gradually over the quarter. The 13F alone won't tell you which.
• If this fund held $500 million of the same stock in the prior filing, this quarter's $450 million represents roughly a 10% reduction in position size -- but knowing that requires actually comparing this filing against the last one, since a single filing is a snapshot, not a change log.
• Sole investment discretion means this manager alone decided to buy this stock; shared discretion would mean another party had a say (common in some fund-of-fund or advisory structures).
• The market value reflects the stock's price at quarter-end, not today. If the stock has moved 20% since the filing date, the dollar figure in the 13F is already stale -- the share count is the more durable piece of information.

This kind of quarter-over-quarter comparison is tedious to do by hand across even a handful of managers, let alone thousands -- which is exactly why a tool that automatically diffs one quarter's 13F against the last one is far more useful than reading a single raw filing in isolation.

Quick answers to common questions

Is a 13F the same as a 13D or 13G? No. 13D and 13G are separate filings triggered when any single holder -- institutional or individual -- crosses 5% ownership of a specific company's shares, regardless of overall portfolio size. A 13F is about a manager's overall U.S. equity book crossing the $100 million threshold; 13D/13G is about ownership concentration in one company.

Does a 13F apply to foreign investment managers? Yes, if they meet the $100 million threshold and use U.S. jurisdiction-based trading in qualifying securities -- nationality of the manager isn't the deciding factor, the securities and the assets under management are.

Where can I see short positions or options exposure, then? There's no equivalent public quarterly filing for short positions specifically -- some jurisdictions outside the U.S. require short-position disclosure at certain thresholds, but the U.S. doesn't for equities the way it does for longs via 13F. Basic call/put options do show up on a 13F, but complex derivatives and most hedging structures don't.

Why do some famous investors seem to have 13F-only portfolios that look surprisingly simple? Often because a large share of their capital sits in exactly the securities 13F covers (U.S. common stock), so their filing genuinely does capture most of what they're doing. Others run much more complex, multi-asset books where the 13F is a much smaller slice of the full picture -- there's no way to tell which situation you're looking at from the filing alone, which loops back to the core lesson of this guide: a 13F is real data, not the whole story.

The bottom line

A 13F filing is a quarterly, SEC-mandated disclosure of a large institutional manager's U.S. long equity positions -- genuinely useful, publicly available, and free, but partial and delayed by design. Understanding both halves of that sentence is what separates using 13F data well from being misled by a headline built on top of it.