How to Read a 13F Filing: Track What Hedge Funds and Buffett Are Buying

13F Filings at a Glance

What a 13F Actually Is

A Form 13F is a quarterly disclosure required by Section 13(f) of the Securities Exchange Act of 1934. Any institutional investment manager — hedge fund, mutual fund, pension fund, insurance company, or bank trust department — that exercises investment discretion over $100 million or more in "13(f) securities" (a list of roughly 5,000-plus mostly US-exchange-listed stocks, some ETFs, and select convertible instruments that the SEC updates quarterly) must file one within 45 days of each quarter's end.

The filing itself is a plain table: each row lists a security (by name and CUSIP number), the number of shares held, and the market value as of quarter-end. There's no explanation of why the fund bought or sold anything — just the raw numbers.

Step by Step: Finding a 13F on SEC EDGAR

• Go to SEC EDGAR's company search at sec.gov/cgi-bin/browse-edgar and search for the fund's name (e.g. "Berkshire Hathaway") in the company name field.
• In the results, find the entity matching the fund's investment management arm (large firms sometimes have several related entities — look for the one that files 13F-HR forms, not 10-Ks or other filings).
• Filter the filing type field to "13F-HR" and click Search — this returns every quarterly filing that fund has made, most recent first.
• Open the most recent filing and click into the "INFORMATION TABLE" document (not the cover page) — this is the actual holdings list with shares and values.
• To see what changed, open the prior quarter's filing the same way and compare share counts line by line — EDGAR doesn't do this for you natively.

"13F" gets used as a catch-all for "SEC ownership filing," but the SEC runs several distinct disclosure regimes that answer different questions. Confusing them is the fastest way to misread what you're looking at.

The practical difference: a 13F tells you a fund's overall positioning across every 13(f) security it holds, while a 13D or 13G tells you about ownership in one specific company, and a Form 4 tells you about one insider's trade. A single stock can show up in all four at once from different filers — none of them contradicts the others; they're answering different questions.

Worked Example: Reading a Position Change

Say a fund's Q1 2026 13F shows 2,000,000 shares of a stock, and its Q2 2026 13F shows 3,500,000 shares of the same stock. Here's what that comparison tells you — and doesn't:

The filing won't tell you at what price the fund bought those extra shares, whether it has since sold them (the next 45-day-delayed filing is your only way to find out), or whether it's simultaneously short the same stock through a vehicle not covered by 13(f) reporting.

A Real 13F, Decoded: Inside Berkshire Hathaway's Filing

The raw EDGAR table for Berkshire Hathaway lists roughly 45 CUSIP rows with no names attached. Here's what that table actually reveals once translated into holdings and thesis — the top of Berkshire's concentrated, ~$330B equity portfolio:

Notice what the table alone can't tell you: Berkshire also disclosed a ~$330B cash and T-bill pile in the same period — money sitting on the sidelines that no 13F line item captures, since 13Fs only report equity positions, never cash. Reading the filing without that context would make Berkshire look far more fully invested than it actually is. For the full breakdown of every top-10 position and what changed last quarter, see our Warren Buffett Portfolio 2026 guide.

Financial media loves the headline "[Fund] just bought [stock]" — but the filing alone rarely supports the trade idea the headline implies. Run through these five questions before treating a 13F as a signal:

• How old is this filing, exactly? Check the quarter-end date, not the filing date — a 13F filed today could reflect a position from 3½ months ago.
• Is this a new position, or a rebalance of an existing one? A fund adding 5% to a position it's held for a decade is very different news from a brand-new stake.
• How large is the position relative to the fund's total portfolio? A $50M position tells you little about a fund managing $50B; a position that's 10%+ of the portfolio reflects real conviction.
• Could this be an index fund, ETF sponsor, or market maker rather than an active bet? Passive managers file 13Fs too, and their "buying" is often just inflows, not a view on the stock.
• What's the fund's known holding period and philosophy? A quant fund that turns over its book monthly and a value fund that holds for a decade are giving you very different kinds of information from the same form.

What a 13F Can't Show You

• Short positions — 13Fs are long-only disclosures; a fund's short book (however large) never appears.
• Non-US-listed foreign stocks and most bonds/commodities — only Section 13(f)-listed securities are reportable.
• Private company stakes, real estate, and pre-IPO holdings — none of that is a 13(f) security.
• Exact trade timing or price paid — only the quarter-end snapshot of shares and market value.
• The fund's reasoning — 13Fs are pure numbers, no commentary or thesis included.
• Real-time changes — a position could be fully exited the day after quarter-end and still show as "held" on the filing you're reading 45+ days later.

Bottom Line

13F filings are one of the few free, mandated windows into what the largest institutional investors — including Warren Buffett's Berkshire Hathaway — are doing with their US equity portfolios. Used correctly, they're a great way to understand a fund's sector tilts, conviction levels, and long-term philosophy shifts over multiple quarters.

Used incorrectly — as a real-time trading signal to copy — they're stale, incomplete (no shorts, no reasoning, no price), and have a track record of underperforming simpler approaches. Read 13Fs for insight into how the best investors think, not for a shortcut to their next trade.

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