SEC Form 144 Explained: The Insider Intent-to-Sell Notice

If you follow insider activity through Form 4 filings, you are watching the transaction afterit happens. There is a filing that sits earlier in that chain—one that tells you an insider intends to sell, before the trade ever executes. That filing is the sec form 144 filing, formally titled “Notice of Proposed Sale of Securities.” The word “proposed” is the operative one. No transaction has occurred yet when a Form 144 lands on EDGAR.

The financial press routinely reports Form 144 filings as “insider sells stock.” Wall Street Mojo’s reference on Form 144 calls this out directly: Form 4 reports transactions that have already occurred; Form 144 announces transactions that have not yet occurred. Conflating the two is one of the most common errors in retail investor analysis of insider selling.

This guide covers what Form 144 actually discloses, the legal framework that requires it, why it was invisible to investors for most of its history, and how a February 2026 academic study of 2.6 million matched transactions changed what we know about the filing’s reliability as a signal.

What Form 144 Actually Is (And What It Is Not)

Form 144 is a notice—not a confirmation. When a corporate affiliate or holder of restricted securities wants to sell shares into the public market, SEC rules require them to put the world on notice of that intention before, or simultaneously with, placing the sale order. The Washington Service’s analysis of Form 144 is precise on this point: the filer “is permitted, but not required, to sell the restricted shares at any time within 90 days after filing.”

This is the distinction that trips up casual readers. A headline like “CEO files Form 144 for 500,000 shares” does not mean the CEO sold 500,000 shares. It means the CEO filed notice of a proposed sale that may or may not happen over the next three months. The sale, if it occurs, will later appear on a Form 4. A Form 144 with no corresponding Form 4 means the sale never happened.

Form 144 also provides coverage that Form 4 does not: it captures insider selling activity at foreign private issuers that are not required to file Form 4. Officers and directors of foreign issuers traded on U.S. exchanges must register proposed sales of restricted stock on Form 144 even when they face no Section 16 filing obligation. For investors following companies like Spotify or Baidu, Form 144 has historically been the only insider-activity disclosure available.

Why Form 144 Exists: The Rule 144 Safe Harbor

Restricted securities are shares acquired outside of a registered public offering— through private placements, employee compensation plans, or other exempt transactions. Control securities are shares held by a company’s affiliates (officers, directors, and 10%-plus shareholders) regardless of how they were acquired. Both categories face legal restrictions on resale into the public market.

Rule 144 is the SEC’s safe harbor that allows affiliates and restricted-security holders to sell these shares without registering the transaction, provided they satisfy five conditions. NASPP’s guide to Rule 144 lays these out clearly:

Form 144 is the fifth condition—the notice that activates the safe harbor for larger sales. Without it, an affiliate attempting to sell a significant block of restricted or control securities would be selling unregistered securities into the public market without the legal protection Rule 144 provides.

Who Must File and When

Not every insider sale requires a Form 144. Toppan Merrill’s guide to Form 144 requirements sets out the threshold: a Form 144 is required when planned sales in a rolling three-month period exceed 5,000 shares or $50,000 in aggregate value. Sales below those thresholds can proceed without a filing.

The filers fall into two categories: affiliates selling any securities of the issuer (not just restricted ones), and non-affiliatesselling restricted securities they have held for less than one year. Once a non-affiliate satisfies the holding period, they generally sell freely without Rule 144’s volume or notice conditions.

The filing deadline is strict. Verity’s analysis of Form 144 disclosure requirements confirms that the form can be filed up to 10:00 pm ET on the day the sale order goes to the broker. The filing must be concurrent with or prior to placing that order—not the next morning, and not after the trade executes. This tight window is why Form 144 sometimes appears the same day as the corresponding Form 4.

What the Form Discloses: Field by Field

A Form 144 is a short document. Its key fields are worth knowing because they differ meaningfully from what Form 4 discloses.

That last field — broker information — does not appear on Form 4 at all. The Washington Service notes that this broker data enables deeper analysis: researchers and institutions can track which brokers handle large insider block trades, revealing patterns in how affiliates route their sales. For most retail investors this field is secondary, but for quantitative analysis it adds a dimension Form 4 cannot provide.

The “prior sales in 3 months” field is also useful. It tells you whether the current proposed sale is the first in a series or part of an ongoing program— context that would require cross-referencing multiple Form 4 filings to reconstruct from scratch. On a Form 144, it is declared directly.

The 90-Day Window and Why Sales May Never Happen

Once a Form 144 is filed, the insider has 90 days to sell any portion, all, or none of the proposed shares. 2iQ Research’s overview of Form 144 is explicit: sellers “are not obligated to sell” after filing. If the 90-day window closes without a sale, the Form 144 simply expires. No cancellation notice is required. No public acknowledgment that the proposed sale did not happen.

A February 2026 study published on arXiv quantified exactly how large this problem is. The paper — “The Information Dynamics of Insider Intent” — covered 2.6 million matched Form 144 and Form 4 transactions across 111,800 unique insiders from 2003 through 2025. Its machine-learning audit found a 52.4% opacity rate: aborted Form 144 signals (where no corresponding Form 4 sale appeared) were statistically indistinguishable from routine executions across ten or more algorithmic architectures. The models could not reliably tell the difference between a Form 144 that led to a sale and one that expired unused.

How Form 144 Found EDGAR: The 2022–2023 Rule Change

For most of its existence, Form 144 was a paper document. Affiliates mailed or faxed it to the SEC; staff processed it at SEC offices; and after 90 days, the physical form was destroyed. No digital archive. No public database. The form was technically public—you could request to see it in person at an SEC reading room—but practically inaccessible to any investor who was not physically present in Washington.

COVID-19 made this arrangement untenable. When SEC offices closed in April 2020, paper Form 144s could not be received or processed. A gap in the record opened that ran until the offices reopened in June 2022. Verity’s documentation of the disclosure changes captures the scale of the data gap the pandemic created and the pressure it placed on the SEC to modernize the form.

The SEC responded with Release 33-11070. Effective April 13, 2023, all Form 144 filings must be submitted electronically through EDGAR in XML format. Verity’s documentation of the disclosure changes notes that before the mandate only a small percentage of eligible filings were available digitally, and most of those were in PDF format rather than structured data—making them practically inaccessible. The rest existed on paper, in offices, before being discarded after the 90-day window closed.

The shift to EDGAR created, for the first time, a searchable, real-time stream of Form 144 filings that any investor could access. The alignment of the filing deadline with Section 16 reporting also changed: beginning March 20, 2023, Form 144 can be submitted until 10 pm EST, matching the Section 16 filing window for Forms 3, 4, and 5.

Form 144 vs. Form 4: Reading Both Together

The two forms cover different moments in the selling sequence and disclose different things. Understanding the gap between them is where the analytical value lives.

The 2026 arxiv study uncovered a structural issue that inverts the expected sequence. Rather than Form 144 preceding Form 4 as a true forward-looking signal, the researchers found that trade execution (Form 4) frequently precedes public notice (Form 144)—a “reporting inversion.” The study identified a 1.65% cumulative market excess return during the filing gap (t=553.93, p<0.001), suggesting that the market absorbs information from the actual trade before the Form 144 reaches public view.

The practical implication: for retail investors who can see both filings in real time, Form 4 remains the faster and more reliable signal for confirmed selling. But Form 144 provides indispensable context about the nature of the shares being sold—whether they are restricted securities from a private placement, compensatory grants from years ago, or control securities held for decades— context that Form 4 alone does not supply.

Signal vs. Noise: When Form 144 Matters Most

Not all Form 144 filings carry the same analytical weight. Understanding which cases carry genuine signal helps filter the roughly 60% of insider sales that are routine pre-planned transactions motivated by liquidity and diversification rather than negative information about the company.

Cases where Form 144 carries genuine signal

Large proposed blocks by C-suite insiders.A CEO or CFO filing to sell a substantial percentage of their total stake—particularly a stake built primarily through open-market purchases rather than compensation grants—is a different event than a director trimming a position for diversification. Patterns of executive selling visible through Form 144 can create downward pressure on the stock through supply-and-demand dynamics alone, even before the Form 4 confirms what actually traded.

Foreign private issuers. For companies like Spotify, Baidu, or other foreign-listed equities where Form 4 was historically unavailable, Form 144 provides visibility into insider activity that exists nowhere else in public disclosures. This use case remains relevant even after the March 2026 HFIAA expansion that brought many FPI insiders into Form 4 reporting, because affiliate non-directors at FPIs still fall outside the new Section 16 requirement.

First sales following lockup expiry.When a company’s lockup period ends—typically 180 days after an IPO—restricted insiders become eligible to sell for the first time. Form 144 filings in the weeks immediately following lockup expiry can indicate whether key founders and early investors plan to distribute their positions, which has historically coincided with post-lockup price pressure.

Cases where Form 144 is noise

Tax-driven sell-to-covers.When RSUs or options vest, the company withholds a portion of shares to cover the employee’s tax liability. This generates an automatic sale—one the insider had no discretion over. On Form 4 these appear as transaction code F. On Form 144 they are often indistinguishable from discretionary sales. Verity notes this directly: tax-driven sell-to-cover transactions appear identical to discretionary sales on Form 144, creating noise.

Routine diversification by founders with large positions.A founder who holds 20 million shares accumulated before the company went public and who files Form 144 to sell 500,000 shares is reducing a 2.5% position. That is portfolio management, not a directional statement about the company’s prospects.

Pre-planned 10b5-1 program sales.Many Form 144 filings are associated with Rule 10b5-1 trading plans set up months in advance. When a Form 4 discloses that the corresponding sale was “pursuant to a Rule 10b5-1(c) plan,” the Form 144 that preceded it carries limited informational content about how the insider felt about the stock at the time of the proposed sale notice.

How to Find Form 144 Filings on EDGAR

Form 144 filings became searchable on EDGAR after the April 2023 electronic mandate. The workflow for finding them is straightforward, though slightly different from the path used for Form 4 data.