What Is the IPO 90-Day Rule? A Complete Guide

If you've ever bought shares in a hot new company right after its IPO, you've probably heard traders whisper about the "90-day rule." Maybe you've seen headlines warning of a looming "lock-up expiration" and wondered if you should sell everything before the floodgates open. Let's cut through the noise. The so-called "90-day rule" is actually a common shorthand for the IPO lock-up period, a contractual restriction that prevents company insiders from selling their shares immediately after the company goes public. But here's the twist everyone gets wrong: it's rarely exactly 90 days. It's typically 180 days. The "90-day" label is a bit of a market misnomer, but it sticks because it captures the essence of a critical post-IPO phase where the first wave of insider selling can become possible.

Understanding this rule isn't just academic. It directly impacts your investment. When a lock-up expires, millions of previously restricted shares can hit the market. This potential supply shock can—and often does—put downward pressure on the stock price. I've watched this play out dozens of times. Sometimes it's a non-event; other times, it's a 20% drop in a week. The difference often comes down to the specifics that most casual investors gloss over.

What Exactly Is the IPO Lock-Up Period?

Think of it as a cooling-off period. When a company files for an IPO with the SEC, the lead underwriters (like Goldman Sachs or Morgan Stanley) require key shareholders to sign a lock-up agreement. This is a legal contract, not a suggestion. It explicitly forbids them from selling, hedging, or otherwise transferring their shares for a set period following the IPO date.

The standard length is 180 calendar days. I can't stress this enough. While "90-day rule" is the common phrase, the boilerplate language in most underwriting agreements sets it at six months. You'll sometimes see 90 days for smaller deals or special cases, but 180 is the market norm. The count starts from the IPO pricing date, not the first trading day.

Who is Bound by the Lock-Up Agreement?

It's not just the CEO. The net is cast wide to cover virtually everyone with substantial pre-IPO equity. If you're investing in a newly public company, you should know who's sitting on a pile of locked-up shares.

• Company Executives & Employees: The CEO, CFO, other C-suite members, and typically all employees holding stock options or RSUs.
• Early Investors & Venture Capitalists: This is the big one. VC firms that funded the company's early rounds (Series A, B, C, etc.) are major holders. Their lock-up expiration is often the most anticipated event, as they may be looking to return capital to their own investors.
• Founders and Large Pre-IPO Shareholders: Anyone owning a significant stake (usually 1% or more) before the offering.
• The Company Itself: While the corporation can't sell its own treasury shares during this time, it's also restricted from issuing new shares that could dilute existing holders, barring certain exceptions.

The public investors like you and me who buy shares on the open market on day one? We are not bound by any lock-up. Our shares are freely tradable from the moment we buy them. This creates a two-tier market: a small float of public shares trading wildly, and a massive iceberg of locked-up shares waiting beneath the surface.

Key Provisions and Fine Print You Must Know

This is where most online explanations stop, but the devil is in the details. The lock-up agreement isn't a simple on/off switch. It has clauses that can trip up even seasoned investors.

The "Early Release" or "Leakage" Clause

Many agreements allow the underwriter to grant an early release to some insiders before the official expiration date. This isn't automatic; it's at the underwriter's sole discretion, often based on the stock's trading performance. If the stock has done well and there's strong investor demand, the bank might let a few key executives sell a small portion (say, 10-15%) of their holdings early. This can be a positive signal, but it also introduces supply earlier than the market calendar indicates.

SEC Rule 144: The Rule That Governs the Actual Sales

Here's the critical link everyone misses. The lock-up agreement expires, but that doesn't mean insiders can dump all their shares the next morning. Their sales are still governed by SEC Rule 144, which imposes conditions on the sale of "restricted" and "control" securities.

After the lock-up ends, insiders must typically comply with Rule 144's requirements, which include:

• Volume Limitations: They can only sell a quantity equal to the greater of 1% of the outstanding shares or the average weekly trading volume over the past four weeks.
• Form 144 Filing: They must file a Form 144 with the SEC when they intend to sell, declaring the number of shares to be sold. This filing is public and gives the market a heads-up.
• Manner of Sale: Sales are usually made through a broker in ordinary brokerage transactions.

So, the expiration of the lock-up starts the clock on Rule 144 compliance; it doesn't trigger an instantaneous, unrestricted fire sale. This staggered selling is why the price pressure can sometimes last for weeks or months, not just a single day.

Why Does This Rule Exist? (The Real Reason)

You'll hear the standard line: "It's to protect investors." That's true, but let's be more specific. The underwriters impose it for two hard-nosed, practical reasons:

1. To Ensure IPO Success: Imagine if the founders and VCs could sell 50% of their holdings on the first day of trading. The market would be instantly flooded with shares, likely crashing the price and dooming the offering. The lock-up guarantees a period of market stability, allowing the underwriter to establish an orderly trading market for the new stock. It's a show of confidence—insiders are saying, "We believe in this company's long-term value, so we're not running for the exits immediately."
2. To Manage Perception and Align Interests: It aligns the interests of insiders with new public shareholders, at least for six months. If the stock tanks because of poor execution, the insiders feel the pain right alongside you. It prevents a scenario where insiders cash out massive fortunes at the IPO pop while leaving public holders holding the bag if the business falters.

From the SEC's perspective, it supports market integrity by preventing manipulative schemes that could arise from immediate, massive insider selling.

A Real-World Case Study: Snowflake's Lock-Up

Let's make this concrete. Snowflake (SNOW) had a blockbuster IPO in September 2020. Its lock-up period was the standard 180 days, set to expire in March 2021.

Snowflake's case shows that a massive unlock doesn't always spell disaster. The stock had run up tremendously post-IPO, so a pullback was expected. Because the expiry was well-telegraphed, the market had time to digest the information. The early release for executives also acted as a pressure valve. By the time the full expiry hit, much of the nervous selling was already done.

What Actually Happens After Lock-Up Expires?

The narrative is that the stock always tanks. The reality is more nuanced. The outcome depends on a mix of factors:

• Company Performance: If the company has smashed its first few earnings reports, the selling might be minimal. Insiders are less motivated to sell a winning horse.
• Overall Market Sentiment: In a bull market, the impact is often muted. In a bear market, it can exacerbate declines.
• Insider Intent: Are VCs desperate for liquidity to fund new investments? Do executives need to sell for tax purposes? Market rumors and subsequent Form 144 filings give clues.
• Float Increase Size: How many shares are unlocking relative to the existing float? A 200% increase is scarier than a 20% increase.

Often, the most significant price move happens in the week or two before the expiration, as anticipatory selling by public investors takes place. The actual expiration day can sometimes be a relief rally if the feared selling doesn't materialize immediately.

An Investor's Strategy Before and After Day 90 (or 180)

So, what should you do? Blindly selling before every lock-up expiry is a recipe for missing out on great companies. Here's a more measured approach I've used.

Before the Expiry:

• Mark Your Calendar: Know the exact date. It's in the company's S-1 filing. Don't rely on financial news to remind you.
• Assess the Context: Is the stock already down 30% on bad news? The lock-up sell-off might be less severe. Is it up 150% on hype? The risk is higher.
• Consider Taking Partial Profits: If you have a large gain, selling a portion (e.g., 25-30%) ahead of the expiry locks in profit and reduces risk. It's not an all-or-nothing game.

After the Expiry:

• Don't Panic Buy or Sell on Day 1: Wait. Let the market absorb the new supply. The selling pressure can last for several weeks as insiders file their Form 144s and execute planned sales.
• Watch the Volume and Form 144 Filings: Are insiders selling in huge blocks? Or are sales trickling out? The SEC's EDGAR database is your friend here.
• Re-evaluate the Fundamentals: Once the lock-up overhang is gone, the stock often starts trading more on business fundamentals than technical supply constraints. This is when you can get a clearer picture of its true value.

I made the mistake early in my career of selling a fantastic software stock the day before its lock-up expired, only to watch it climb steadily for the next year. The company's execution was flawless, and insiders sold only a tiny fraction of their holdings. I learned that the rule is a risk factor, not a destiny.

Your Top Questions on the IPO 90-Day Rule, Answered