The short answer
A 13F filing is a quarterly disclosure that the SEC requires from any institutional investment manager with at least $100 million in US stock holdings. It lists every long position the manager held at the end of the quarter, the number of shares, and the dollar value of each position. The filing is due 45 days after quarter-end and is publicly available on the SEC's EDGAR database.
That's the technical answer. The interesting answer is what these filings let you do: see exactly what some of the world's most successful investors are holding, every three months, for free.
The rule's history
The 13F requirement came out of a 1975 amendment to the Securities Exchange Act. Congress wanted more transparency in how institutional money was being deployed, partly to track market influence, partly to give the public a window into how the largest pools of capital were positioned. The rule applies to anyone managing over $100M in qualifying US securities, which sweeps in:
- Hedge funds
- Mutual funds
- Pension funds
- University endowments
- Insurance companies
- Family offices over the threshold
If you've ever seen a headline like "Warren Buffett bought $X billion of Y," it almost certainly came from reading Berkshire Hathaway's 13F.
What a 13F includes
Every 13F lists, for the end of the previous quarter:
- The security name and ticker for each long equity position
- CUSIP (the standardized identifier for the security)
- Number of shares held
- Market value of the position at quarter-end
- Investment discretion (sole, shared, or none)
- Voting authority (sole, shared, or none)
The format is standardized, machine-readable, and free. If you go to SEC EDGAR and search for any major fund, you can read their 13F directly.
What a 13F does NOT include
This is where most beginners get tripped up. 13Fs have meaningful blind spots:
Short positions are not disclosed. A fund could be long Apple in their 13F and short an equal dollar amount of Apple via swaps without any of it showing up. This means a 13F is an incomplete picture of a fund's actual market exposure.
Cash and bonds aren't included. 13Fs are for US-listed equities only. A fund with 60% of its book in Treasuries looks the same as one with 100% in stocks, when you read just the 13F.
International stocks aren't included. Securities listed on foreign exchanges don't show up. ADRs of foreign companies do.
Derivatives are partially included. Options, swaps, and futures positions appear only in some cases and are reported in confusing ways.
The data is up to 45 days old. A 13F filed in mid-November shows the fund's positions as of September 30. By the time you read it, the manager may have already exited positions you're seeing for the first time.
Why smart investors read them anyway
Despite the blind spots, 13Fs are still one of the most useful free resources in retail investing. Here's why.
The 45-day delay matters less for long-term holders. If you're following Warren Buffett, who typically holds positions for years, a 45-day delay is rounding error. For a quant fund that turns over weekly, a 13F is useless. For a value-oriented holder, it's gold.
Position sizing tells you conviction. A 5% position in a $100B portfolio is a different signal than a 0.1% position. 13Fs let you see the relative weights, which is often more useful than the names alone.
Quarter-over-quarter changes are visible. When a fund adds a new position, doubles an existing one, or exits entirely, those changes are detectable by comparing consecutive filings. Most of the value in 13F analysis comes from these change signals, not from snapshots.
You can identify managers worth following. Once you find managers whose track record and style you respect, their 13Fs become a curated source of stock ideas. You don't need to do all the original research; you can stand on the shoulders of someone whose research culture and incentives you trust.
How we use 13Fs at Advising Alpha
The portfolios at Advising Alpha are original creations. Decades of research and trial-and-error went into them, and the construction is ours. But 13F filings are one of the more important inputs in the process, because they tell us something nothing else does: where the institutional flow is going.
That matters because of one of the harder lessons we've learned over the years. You can find a great company on fundamentals alone, build conviction, invest, and watch the stock go nowhere for a year or more. The thesis was right. The math was right. The stock just sat there. Why? No flow of big money was hitting it. Without institutional buying, even great companies tread water.
Money flows where it's treated best. 13Fs are how you see the flow before it's fully reflected in price.
So our process combines several inputs, not just 13Fs:
- Fundamentals research first. Quality businesses, durable cash flows, reasonable valuations, sector spread. The basics that any disciplined investor has to do.
- 13F flow signal. For names we like on fundamentals, we look at whether high-quality managers are also accumulating. When the answer is yes, the wave is forming.
- Our own quality and valuation filters. Once we have a candidate list, we apply additional criteria — fundamentals quality, valuation discipline, industry diversification — to narrow to the final portfolio.
- Active risk management. Most managers don't apply this layer at the level we do. Drawdown discipline, sector limits, rebalance bands. The "don't blow up" overlay.
- Rebalance quarterly. When new 13Fs come out (45 days after each quarter), we re-run the analysis with the fresh institutional-flow data and rebalance accordingly.
This is meaningfully different from "13F cloning" — the practice of literally copying one manager's portfolio. We don't clone any single manager. The portfolios are blends of fundamental conviction and institutional-flow confirmation, with our own filters and risk management on top.
The one explicit exception is Tepper Tactical, our portfolio inspired by and refined from David Tepper's strategy. Even there, we add our own active risk-management overlay, so it's not a direct clone. Just the closest of the three to a single-manager-tracking model.
A brief history of 13F-driven investing
The idea that retail investors should pay attention to 13Fs caught on broadly in the 2000s, helped by services like Whalewisdom and Insider Monkey that aggregated and visualized the data. Before then, you'd have to read EDGAR XML by hand.
Academic research has consistently found that carefully selected 13F-following strategies generate alpha. The original 1990s work by Joe Lakonishok and others found that following the picks of high-quality value managers produced market-beating returns over multi-year windows. Subsequent studies have shown the effect is real but depends heavily on which managers you follow and how you weight their picks. Following everyone is noise; following the right people is signal.
What this means for you
If you're a retail investor, here's how to use 13Fs in practice:
Don't blindly clone. Even Warren Buffett's 13F has stocks that don't make sense for an individual investor's portfolio (concentration, tax considerations, position size relative to your wealth). Use them as research input, not as a copy-paste.
Focus on changes, not snapshots. New positions and meaningful adds are higher signal than existing positions you've seen for years. Most successful 13F-driven strategies emphasize quarter-over-quarter delta.
Filter by manager quality. The 13F universe includes thousands of filers. Ten of them are worth your attention. The rest are noise. Build a watchlist of high-quality managers and ignore the rest.
Combine with valuation discipline. A 13F tells you what someone smart owns; it doesn't tell you whether the price you're paying today is fair. Always layer your own valuation work on top.
That's the philosophy behind Advising Alpha — combining fundamentals research with the institutional-flow signal you can only get from 13Fs, and adding our own filters and active risk management on top. You can see the result on the portfolio pages.