13F Filing Season Guide: What to Watch and When

What Is 13F Filing Season?

Four times a year, every institutional investment manager with more than $100 million in qualifying assets must disclose their equity holdings to the SEC. These disclosures—called 13F filings—give retail investors a window into what the biggest funds on Wall Street have been buying and selling.

The period when these filings pour in is known as 13F filing season. It's one of the most closely watched events in the investing calendar, and for good reason: it's the only time you can see exactly what firms like Berkshire Hathaway and Pershing Square Capital Management held at the end of each quarter.

At 13F Insight, we track over 380,000 13F filings from more than 9,000 institutional filers dating back to 1999. In this guide, we'll walk you through the filing calendar, what to look for each season, and how to use 13F Insight to stay ahead of the curve.

The Filing Calendar

13F filings are due 45 days after the end of each calendar quarter. Here's the annual schedule:

Most filings land in the final two weeks before the deadline, with a burst of activity on the deadline day itself. Some high-profile filers consistently file right at the deadline—or even a day or two late.

Current season: We're at the tail end of Q4 2025 filing season. The report date is December 31, 2025, and the filing deadline was February 14, 2026. Most major filers have already reported, but late filers and amendments continue to trickle in.

What Happens During Filing Season

The 45-day filing window creates a predictable rhythm each quarter:

Early Filers (Days 1–20)

A small number of managers file well before the deadline. These tend to be smaller firms or those with automated compliance processes. Early filings can offer an initial glimpse into market sentiment, but the most-watched names rarely appear this early.

Deadline Filers (Days 35–45)

The majority of filings arrive in the final 10 days. This is when the big names—Berkshire Hathaway, Bridgewater, Citadel, Renaissance Technologies—typically appear. The SEC's EDGAR system can see hundreds of filings per day in this period.

Late Filers (After the Deadline)

Some managers miss the deadline entirely. Late filings are surprisingly common: on February 23, 2026, for example, we're still seeing Q4 2025 filings from firms like REX Advisers LLC, Continental Investors Services, and IronBridge Private Wealth. Occasionally, a firm will file extremely late—Leonteq Securities AG recently filed for both Q1 2025 and Q4 2024, more than six months past their respective deadlines.

What to Watch For

Not all 13F changes are equally interesting. Here's what experienced investors focus on during filing season:

New Positions

When a major fund opens an entirely new position, it signals conviction. Look for well-known investors initiating stakes in companies they've never held before—this often generates the most market discussion.

Complete Exits

A fund selling out of a position entirely can be just as revealing as a new buy. If multiple large institutions exit the same stock in the same quarter, it's worth investigating why.

Significant AUM Swings

Changes in a fund's total assets under management (AUM) can indicate broader market positioning. Berkshire Hathaway's AUM, for instance, tells a story across quarters:

• Q1 2024: $331.7B → Q2 2024: $280.0B (significant reduction)
• Q3 2024: $266.4B → Q4 2024: $267.2B (stabilizing)
• Q1 2025: $258.7B → Q2 2025: $257.5B (continued trimming)
• Q3 2025: $267.3B → Q4 2025: $274.2B (building again)

Concentration Changes

Watch how concentrated or diversified a fund's top holdings become. A fund moving from 50 positions to 42—as Berkshire did in Q4 2025—suggests increased conviction in fewer names.

Whale Score

On 13F Insight, each filer has a Whale Score that helps you quickly identify high-quality institutional investors. During filing season, sorting by Whale Score lets you focus on the filings that matter most.

Case Study: Berkshire Hathaway's Q4 2025 Filing

Let's walk through a real filing to see what a filing season analysis looks like in practice.

Berkshire Hathaway filed its Q4 2025 13F-HR on February 17, 2026—three days after the deadline. (Warren Buffett's firm routinely files right at or just past the deadline, generating anticipation each season.)

Key facts from the filing:

• Report date: December 31, 2025
• AUM: $274.2 billion
• Holdings: 42 positions
• AUM change: Up from $267.3B in Q3 2025 (+2.6%)

The AUM increase from Q3 to Q4 2025 marks the second consecutive quarter of growth after Berkshire spent much of 2024 and early 2025 reducing its equity exposure. The shift from $331.7B in Q1 2024 to a low of $257.5B in Q2 2025 represented a significant de-risking; the rebound to $274.2B suggests renewed buying interest.

You can explore Berkshire's full holdings breakdown, AUM history, and position changes on the Berkshire Hathaway filer page on 13F Insight.

Late Filers and Amendments

Filing season doesn't end cleanly on the deadline. Two types of post-deadline activity are worth understanding:

Late Filings

The SEC does not enforce the 45-day deadline strictly. Many managers file days, weeks, or even months late. While the SEC can issue deficiency notices, there is rarely a penalty for tardiness. This means you should continue monitoring filings well after each deadline.

Amendments (13F-HR/A)

After submitting their initial filing, managers can file an amendment—designated as 13F-HR/A—to correct errors or update their disclosure. Amendments replace the original filing's holdings data. On 13F Insight, we automatically prioritize the most recent amendment, so you're always seeing the corrected data.

How to Track Filing Season on 13F Insight

13F Insight is designed to make filing season easy to follow. Here's how to use the platform effectively:

Latest Filings Feed

Visit the homepage or the filings page to see the most recently filed 13F reports. During peak season, new filings appear hourly. You can sort by filing date to see the freshest data first.

Filer Pages

Each filer has a dedicated page showing their current holdings, AUM history, and quarter-over-quarter position changes. Bookmark your favorite filers—like Berkshire Hathaway or Pershing Square—and check back during filing season to see their latest disclosures.

Stock Pages

Curious who's buying or selling a specific stock? Visit the stock page (e.g., Apple (AAPL) or American Express (AXP)) to see all institutional holders, sorted by position size. During filing season, this view updates as new filings come in.

Whale Score Filtering

Use the Whale Score to cut through the noise. Higher-scoring filers tend to be larger, longer-tenured institutions with more concentrated portfolios—exactly the kind of "smart money" most investors want to follow.

Common Misconceptions

13F filings are powerful, but they come with important caveats that trip up many investors:

The Data Is Already 45+ Days Old

A 13F filed on the deadline reflects holdings from the end of the previous quarter. By the time you see the data, the fund may have already changed its positions. Think of 13F data as a quarterly snapshot, not a real-time feed.

Not All Institutions File 13F Reports

Only managers with $100 million or more in qualifying 13F securities are required to file. Smaller funds, private equity firms, venture capital funds, and those holding only non-13F securities (like bonds or futures) are exempt.

A Filing Doesn't Mean a Current Position

Just because a fund held a stock on December 31 doesn't mean they still hold it when the filing appears in February. Markets move, and so do portfolios. Use 13F data for directional insight, not as a current portfolio mirror.

13F Filings Only Show Long Positions

Short positions, options strategies, and many derivatives are not disclosed in 13F filings. You're only seeing one side of a fund's portfolio. A fund that appears to own a large stock position may be hedged with puts or have a short position elsewhere.

Frequently Asked Questions

When is the next 13F filing deadline?

The next filing deadline is May 15, 2026, for Q1 2026 holdings (report date March 31, 2026). Filings will begin appearing in April, with the bulk arriving in the first two weeks of May.

How quickly can I see new filings on 13F Insight?

13F Insight processes new SEC filings automatically as they're published to EDGAR. During peak filing season, new filings typically appear on the platform within hours of being filed with the SEC.

Should I trade based on 13F filings?

13F data is best used for research and idea generation, not as a direct trading signal. The 45-day delay means positions may have already changed. Instead, use filings to understand what high-quality investors found attractive, then do your own analysis on whether those ideas still make sense at current prices.

What's the difference between 13F-HR and 13F-HR/A?

13F-HR is the original quarterly holdings report. 13F-HR/A is an amendment that corrects or updates the original filing. When a fund files an amendment, it supersedes the original. On 13F Insight, we always display the most recent version so you see the corrected data.

Do 13F filings show international holdings?

13F filings only cover securities on the SEC's official list of 13F securities, which primarily includes U.S.-listed equities, ETFs, and certain convertible securities. Foreign-listed stocks are generally not included, even if the fund holds them. ADRs (American Depositary Receipts) of foreign companies that trade on U.S. exchanges are included.