What Is a Lockup Expiration? Effects on Share Price (2026)

How a lockup works

When a company prepares an IPO, the underwriters ask officers, directors, employees and pre-IPO investors such as venture and private equity funds to sign lockup agreements. Each holder agrees not to sell, pledge or hedge their shares for a set period without the underwriters' consent. The aim is an orderly aftermarket: the underwriters do not want a flood of insider stock hitting a new listing in its first months.

Three features matter most:

1. Length. 180 days after the IPO is common. Some agreements are shorter, some longer, and SPAC mergers often use different terms.
2. Who is bound. Usually most pre-IPO holders. Some small holders or specific share classes may be excluded.
3. Release terms. Many agreements release shares in stages, for example a portion after the first earnings report, or early if the stock trades above a set price for a number of days. The underwriters also usually keep the right to waive the lockup at their discretion.

Lockups are contracts, not SEC rules. The SEC rules that matter come into play once the lockup ends and holders try to sell.

The rules that govern selling after the lockup

Many pre-IPO shares are restricted securities, and many holders are affiliates of the company. Both groups usually sell under Rule 144 (17 CFR 230.144), which sets the conditions for selling without registration. The points below were checked against the current eCFR text.

• Holding period. For a company that has been an SEC reporting company for at least 90 days, restricted securities must be held for at least six months from acquisition. For a non-reporting company, the minimum is one year. Most pre-IPO holders satisfy this long before the lockup ends, so the lockup, not Rule 144, is usually the binding limit.
• Volume limit for affiliates. An affiliate's sales in any three months cannot exceed the greater of 1 percent of shares outstanding or the average weekly trading volume over the four calendar weeks before the Form 144 notice.
• Form 144 notice. If an affiliate plans to sell more than 5,000 shares or more than $50,000 worth under Rule 144 in a three-month period, a Form 144 must be filed when the sell order is placed with a broker.
• Form 4. Officers, directors and holders of more than 10 percent report sales on Form 4 before the end of the second business day after the trade.

The practical effect: affiliate selling is metered by the volume limit, while non-affiliate holders such as many funds past their holding period can sell more freely. Shares registered for resale can also be sold outside Rule 144.

Why the share price can move

The mechanism is supply and demand. Before the lockup ends, the tradable float may be a small fraction of shares outstanding. Afterward, a much larger share count can trade. If even part of that stock is sold over a few days, it can exceed what normal buyers absorb at the current price.

Several things push the effect larger or smaller:

Two points are easy to miss. First, the date is published in the prospectus, so short sellers, option traders and long holders can position in advance. Some of the effect can come before the date, not on it. Second, many holders do not sell at all. A founder who owns a large stake may keep it for years. A venture fund may distribute shares to its own investors in kind, which spreads selling decisions across many parties and over time.

A worked example

On the expiration date, the shares eligible to trade rise from about 20 million to about 100 million, five times the prior float. Suppose the holder mix is:

• Founders and executives: 35 million shares, all affiliates.
• Two venture funds: 30 million shares, neither affiliated after the IPO.
• Employees and others: 15 million shares.

The founders, as affiliates, can each sell no more than the greater of 1 percent of outstanding shares (1 million) or average weekly volume (about 7.5 million) in any three months, and they must file Form 144 first. The venture funds are not bound by the volume limit. If they decide to sell 10 million shares over two weeks, that is roughly 1 million shares a day, about two thirds of normal daily volume, added on top of normal selling.

That is the overhang to size: not the 80 million released, but the portion likely to be sold, divided by daily volume. In this case the funds matter more than the founders, because they can sell faster and are more likely to want to.

How to read the holder mix

The holder mix often tells you more than the size of the release. Use the prospectus, the latest proxy statement and beneficial ownership filings.

• If a large share of the released stock sits with venture or private equity funds that have held for many years, expect more willingness to sell or distribute.
• If most of the released stock belongs to founders who remain in management, expect slower, metered selling, often through Rule 10b5-1 trading plans disclosed later.
• If the stock trades below the IPO price, many recent holders are under water and may hold, though early-round investors can still have large gains.
• If the release is staged, look at each tranche separately rather than the total.
• If the underwriters granted an early waiver for a secondary offering, the supply may already have been placed with new holders before the date.

A follow-on or secondary offering timed near the expiration is common. It moves locked shares to new holders in one priced transaction, which can replace a scattered open-market overhang with a single discount.

Timeline: what to check and when

A lockup date belongs on a catalyst calendar next to earnings and other dated events. Rising short interest into the date is one sign of positioning; short interest and days to cover explains how to read it, and the 10 best short interest data tools covers where to get it.

Where this goes wrong

• Treating the date as a forced sale. Nobody has to sell. The release only removes a restriction. A stock can rise through its lockup date if demand is strong or if positioning was heavy.
• Sizing the release, not the likely selling. The full number of unlocked shares overstates the overhang. Founders, long-term funds and in-kind distributions spread out selling.
• Missing staged and early releases. A large part of the stock may already be unlocked by earnings triggers, price triggers or waivers. Read the full lockup section, not just the headline period.
• Assuming insider sales signal bad news. After a lockup, funds sell because they have to return capital and employees sell to diversify. A Form 4 sale after a lockup says less than an open-market purchase. The Form 4 guide explains which insider trades carry more signal.
• Ignoring the cost of a short position. Newly public stocks can be expensive to borrow and volatile. A crowded short into a well-known date can reverse quickly.
• Using the wrong share counts. Use shares outstanding and the release schedule from the filings, not a data vendor's float estimate, which may lag.

Dombey's published research reads the lockup terms, holder mix and volume together before any newly listed company it covers; see the research archive.

How a lockup fits with other catalysts

A lockup expiration has a hard date but a soft outcome, a mix explained in hard vs soft catalysts. It rarely stands alone. A newly public company often has its first or second earnings report near the lockup date, and staged releases are frequently tied to those reports. An option market that prices a large move for that week may be pricing both events together, so read implied volatility with the lockup schedule in hand. For spin-offs, a related supply event comes from index funds and holders who receive shares they did not choose; spin-off investing covers that case.

The bottom line

A lockup expiration is the end of a contractual ban on selling pre-IPO shares, commonly 180 days after the offering. It can pressure the price when the released stock is large relative to the float and volume and the holders want to sell, but the date is known in advance and no one is forced to sell. Size the likely selling from the holder mix, Rule 144 limits and release schedule, not the headline share count. Then watch Form 144 and Form 4 filings to see what actually happened.