13F Filings Explained: How to Track What Top Investors Are Buying

Every quarter, the world's most successful investors are required to reveal exactly what they own.

These disclosures are called 13F filings, and they're one of the few windows into how legendary investors actually invest.

Warren Buffett, Bill Ackman, Seth Klarman, Ray Dalio, Michael Burry—all of them must file. And you can see exactly what they're buying and selling.

But there's a catch. If you don't understand how 13F filings work, you'll use them wrong.

What Is a 13F Filing?

A 13F filing is a quarterly report that institutional investment managers must submit to the SEC (Securities and Exchange Commission).

The rule: Any institution managing at least $100 million in qualifying assets must file a 13F within 45 days of each calendar quarter's end.

What's disclosed:

• Every U.S. equity position (stocks and ETFs)
• Number of shares held
• Market value as of quarter end
• Position type (sole, shared, or no voting authority)

What's NOT disclosed:

• Short positions
• International stocks
• Fixed income (bonds)
• Cash positions
• Private investments
• Options (with some exceptions)

Why 13F Filings Matter

1. See What the Best Investors Actually Own

Words are cheap. Holdings are real.

Investors can say anything in interviews. 13F filings show what they actually did with their money.

Example: An investor might talk about being "cautious" on TV while their 13F shows they added to their largest positions. Actions speak louder.

2. Discover New Ideas

Top investors have research teams you don't. They find opportunities before most people.

When a legendary investor takes a new position, it's worth investigating why:

• What do they see that others don't?
• Is this a sector rotation?
• Is this a value play or growth bet?

You're not copying—you're getting a research starting point.

3. Understand Position Sizing

How much conviction does an investor have?

A 15% position tells you something completely different than a 1% position.

4. Track Changes Over Time

The most valuable signal isn't what they own—it's what changed.

• New position: What caught their attention?
• Increased position: Conviction growing
• Reduced position: Taking profits or losing conviction
• Sold out: Thesis broken or target reached

The Legendary Investors You Can Track

13F filings cover thousands of institutions, but certain investors have track records worth following:

Value Investors

Activist Investors

Hedge Fund Managers

Concentrated Investors

How to Use 13F Data Effectively

Step 1: Focus on High-Conviction Positions

Don't look at every position. Look at:

• Top 10 holdings (where the real conviction is)
• New positions (fresh ideas)
• Significant increases (growing conviction)

A fund with 200 positions has many small, meaningless holdings. The top 10 tell the real story.

Step 2: Look for Clusters

When multiple respected investors own the same stock, pay attention.

Example: If Buffett, Klarman, and Ackman all own the same stock, that's more signal than any one of them alone.

This doesn't mean it's a good investment—but it means smart people see something there.

Step 3: Understand the Investor's Style

Match the idea to your own approach.

Step 4: Do Your Own Research

13F data is a starting point, not a finish line.

Before acting on any 13F idea:

1. Understand why the investor might own it
2. Check if the thesis still applies (data is 6+ weeks old)
3. Evaluate whether it fits your portfolio
4. Consider if the price has moved since quarter end

The Critical Limitations of 13F Data

Limitation 1: The Data Is Old

By the time you see a 13F, the information is at least 45 days old—often older.

A lot can happen in 6+ weeks. The investor might have already exited.

Limitation 2: You Only See Long Equity

13F filings don't show:

• Short positions: A fund might be net short even with long holdings
• Hedges: Options strategies that change the risk profile
• Bonds: Fixed income could be the majority of assets
• International: Non-U.S. stocks aren't reported

You're seeing a partial picture.

Limitation 3: You Don't Know Entry Price

Seeing that Buffett owns Apple doesn't tell you:

• When he bought it
• What he paid
• Whether he's up or down
• His target exit price

He might have bought at $30. Buying at $180 is a completely different proposition.

Limitation 4: Position Sizing Matters

A 0.5% position means almost nothing. The fund might be:

• Testing a new idea
• Holding a legacy position
• Required to hold it (index funds)

Only significant positions (>2-3%) indicate real conviction.

Limitation 5: Context Is Missing

You don't know:

• Why they bought
• What thesis they're playing
• How it fits their broader strategy
• When they plan to sell

Two investors can own the same stock for completely different reasons.

Common Mistakes When Using 13F Data

Mistake #1: Copying Blindly

"Buffett bought XYZ, so I will too."

The problem:

• You don't know his cost basis
• The price may have moved significantly
• You don't know his time horizon
• You don't know his thesis

Better approach: Use 13F as a research trigger, not a buy signal.

Mistake #2: Ignoring Time Lag

Acting on 13F data as if it's current information.

The problem: The data is 45-90 days old. The investor might have already:

• Sold the position
• Doubled down
• Changed their thesis

Better approach: Check current price vs. quarter-end price. If it's moved 20%+, the setup has changed.

Mistake #3: Following Too Many Investors

Tracking 50 different funds creates noise, not signal.

The problem: You'll see conflicting positions, endless changes, and no clear direction.

Better approach: Pick 5-10 investors whose style matches yours. Quality over quantity.

Mistake #4: Ignoring Sells

Focusing only on buys and ignoring exits.

The problem: Knowing what investors are selling is just as valuable as knowing what they're buying.

Better approach: Track sold-out positions and significant reductions. These often signal problems you should investigate.

What Position Changes Actually Mean

New Position

An investor initiated a new holding.

Possible meanings:

• Fresh idea from their research team
• Sector rotation play
• Special situation (merger, spinoff)
• Contrarian opportunity

Action: Investigate the thesis. What's the catalyst?

Increased Position

Shares added to an existing holding.

Possible meanings:

• Price dropped and they're averaging down
• Conviction increased
• Position sizing to target weight
• Sector allocation adjustment

Action: More bullish signal than a new position. They already owned it and want more.

Reduced Position

Shares sold from an existing holding.

Possible meanings:

• Taking profits
• Rebalancing portfolio
• Slightly reduced conviction
• Raising cash

Action: Investigate. Small reductions are often just portfolio management.

Sold Out

Position completely exited.

Possible meanings:

• Thesis broken
• Target price reached
• Better opportunity elsewhere
• Risk management

Action: This is a strong signal. Something changed their view entirely.

Building a 13F Monitoring System

What to Track

1. Your focus investors (5-10 max)
2. Their top 10 holdings
3. New positions each quarter
4. Sold-out positions
5. Significant changes (>25% increase/decrease)

When to Check

Filing Season Calendar

Mark these dates—it's when 13F data becomes available:

• February 14: Q4 filings due
• May 15: Q1 filings due
• August 14: Q2 filings due
• November 14: Q3 filings due

Most filers submit close to the deadline, so expect a flood of data in the days around these dates.

The Right Mindset for 13F Investing

Think of 13F data as a research assistant, not an investment advisor.

What 13F data does well:

• Surfaces ideas you might have missed
• Shows where smart money is concentrated
• Tracks conviction changes over time
• Provides a starting point for due diligence

What 13F data doesn't do:

• Tell you when to buy or sell
• Guarantee investment success
• Replace your own analysis
• Account for your personal situation

The best investors use 13F data to generate ideas, then do their own work.

Key Takeaways

13F filings are quarterly disclosures showing what institutional investors own. Any manager with $100M+ must file within 45 days of quarter end.

Why they matter:

• See what legendary investors actually own (not just what they say)
• Discover new ideas from top research teams
• Track conviction through position sizing and changes
• Find clusters where multiple smart investors agree

The critical limitations:

• Data is 45-90 days old by the time you see it
• Only shows long equity (no shorts, bonds, or international)
• You don't know entry price, thesis, or exit plan
• Small positions (under 2%) are often meaningless

How to use them effectively:

• Focus on top 10 holdings and significant changes
• Match investor style to your own approach
• Use filings as research triggers, not buy signals
• Track sells as carefully as buys

The professional mindset:

13F data tells you where smart money is positioned. It doesn't tell you what to do about it.

Use it wisely, and 13F filings become a valuable research tool. Use it blindly, and you're just following someone else's old trades.

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