An IPO lockup is a contract that stops insiders, such as employees, early investors, and founders, from selling shares for a set time after a listing, usually about 180 days. Anthropic’s S-1 uses a staged version instead: most holders are free by the earlier of first-quarter 2027 earnings or day 180, while some stay locked for up to 365 days.
A lockup works like a dam with sluice gates. The water behind the dam is the insiders’ shares, and the gates decide how quickly it reaches the market. A slow, scheduled release lets the level adjust gradually, while a single large release can change the flow at once. Anthropic has built a dam with many gates, and each gate opens on a date that traders can see in advance.
This article is for information only. It is not investment advice or a recommendation to buy or sell any security.
Key takeaways
- A lockup is an agreement that bars insiders from selling for a set period after an IPO. The US Securities and Exchange Commission (SEC) says most last 180 days.
- Anthropic’s S-1 sets a 180-day lockup for most holders, ending at the earlier of 6:00 AM Eastern Time on the second full trading day after first-quarter 2027 results or the 180th day after the prospectus date.
- Holders of more than 0.5% of fully diluted shares and the seven co-founders face a lockup of up to 365 days, ending at the earlier of the second full trading day after third-quarter 2027 results or the 365th day.
- Many holders can sell part of their shares much earlier: up to 10% on the first trading day for non-founder directors, officers and certain employees, and further releases from day 27.
- Business Insider counts 23 separate unlock dates in the year after the IPO, against fewer than 10 for SpaceX.
- Academic research found an average three-day abnormal return of -1.5% around lockup expiries, but that is an average from older IPOs and not a forecast for Anthropic.
- The underwriters can release lockup shares at any time, and the share counts in the S-1 are still blank.
What is an IPO lockup period?
An IPO lockup period is a fixed time after a company lists during which insiders cannot sell their shares. The SEC describes lockup agreements as contracts that bar company insiders, including employees, their friends and family, and venture capitalists, from selling their shares for a set period. It adds that most prevent sales for 180 days, and that some also cap how many shares can be sold in a given window.
Why lockups exist
The purpose is to stop a surge of supply as soon as trading begins. If every early investor and employee could sell on day one, the market would face a large amount of stock before the company had built a public trading record. Wikipedia’s summary of the practice says lockups usually last 90 to 180 days and notes that they have become more complex than the older 180-day rule for everyone.
Who is bound
Employees and pre-IPO investors usually sign agreements when they receive shares or options, and the underwriting banks reaffirm them at the IPO. Employees and early investors tend to want shorter lockups, and the underwriters tend to want longer ones, so the final terms are a negotiated middle ground.
Early release and market standoff agreements
Many modern lockups include early-release clauses that free part of the shares on set dates or after earnings. Some holders are bound by a market standoff agreement with the company instead of a lockup agreement with the underwriters. The effect is the same: the holder cannot sell for the stated period, subject to exceptions.
Why do lockup expiries matter for share prices?
Lockup expiry matters because it can increase the number of shares available to trade. The SEC warns investors that a stock’s price may fall before a lockup ends, as investors anticipate locked-up shares being sold, and tells them to find out whether a recent IPO has a lockup and when it expires.
Academic evidence points the same way on average. Laura Casares Field and Gordon Hanka studied 1,948 IPO lockup agreements in the Journal of Finance (April 2001). They found a three-day abnormal return of -1.5% around expiry, larger for venture-capital-backed firms, and a permanent rise in average trading volume of about 40% once lockups expired. The study covers IPOs from a different era and a much simpler lockup design, so it describes a tendency and does not predict how any one stock will behave.
Anthropic IPO lockup: what the S-1 says
Anthropic made its S-1 public on 26 October 2026 and applied to list Class A common stock on the Nasdaq Global Select Market under the ticker ANT. The lockup terms sit in the “Shares Eligible for Future Sale” and “Underwriting” sections. All of Anthropic’s directors and officers and substantially all of its stockholders are bound by either lockup agreements with the underwriters or market standoff agreements with the company.
The S-1 defines most timing from “the date of this prospectus”, which is the final prospectus issued when the IPO is priced. That date has not been set. Percentages below refer to each holder’s locked-up securities, measured as of a reference date stated in the filing, and the share counts are blank in the current draft.
The four holder groups
| Holder group | Lockup ends at the earlier of | Early releases in the S-1 |
|---|---|---|
| Non-founder directors, officers and certain current and former employees and consultants | The second full trading day after first-quarter 2027 results, or the 180th day | Up to 10% on the first trading day, then up to an additional 35% on the second full trading day after full-year 2026 results |
| Certain other stockholders | The second full trading day after first-quarter 2027 results, or the 180th day | Staged releases from day 27 (see below) |
| Stockholders holding more than 0.5% of fully diluted shares | The second full trading day after third-quarter 2027 results, or the 365th day | Smaller staged releases from day 27 (see below) |
| The seven co-founders | The second full trading day after third-quarter 2027 results, or the 365th day | Up to 29% of their locked-up securities from the earlier of the first-quarter 2027 results trigger or day 180 |
Source: Anthropic S-1, filed with the SEC on 26 October 2026.
Staged releases for certain other stockholders
For the group on the 180-day lockup that is not a director, officer or employee, the S-1 lists these early expirations:
- Up to 6% of locked-up securities on or after each of day 27 and day 48 after the prospectus date.
- Up to an additional 7% on or after each of day 62 and day 76.
- Up to an additional 12.5% on the second full trading day after full-year 2026 results.
- Up to an additional 9.5% on or after each of 13, 27, 41, 55 and 69 days after the full-year 2026 results date.
Taking the filing’s wording at face value, that adds up to 26% released by day 76 and 86% by 69 days after full-year results (VT Markets calculation). The remainder is released at the earlier of the first-quarter trigger or day 180.
Staged releases for holders of more than 0.5%
The group with the longer lockup also has scheduled early releases, though the amounts are smaller:
- Up to 1.8% on or after each of day 27 and day 48, and up to an additional 2.1% on or after each of day 62 and day 76.
- Up to an additional 3.75% after full-year 2026 results, then up to 2.85% on or after each of 13, 27, 41, 55 and 69 days later.
- Up to an additional 4.2% at the earlier of the first-quarter trigger or day 180.
- Up to 5.6% on or after each of 34, 48, 62 and 76 days after first-quarter 2027 results.
- Up to 7.0% after second-quarter 2027 results, then up to 6.3% on or after each of 27, 41, 55, 69 and 83 days later.
On that reading, about 90.9% would be released before the final trigger at the third-quarter 2027 results or day 365 (VT Markets calculation).
Other terms to know
- Company lockup: Anthropic itself has agreed not to sell or issue stock for the period ending at the earlier of the second full trading day after first-quarter 2027 results or day 180, subject to exceptions.
- Underwriter discretion: The representatives of the underwriters can release lockup shares in whole or in part at any time, and some releases can trigger a pro rata release for certain other holders.
- Founder shares sold in the offering: The founders’ lockup applies to their shares other than any shares they sell in the offering under the underwriting agreement.
- Class N shares: Class N common stock converts to Class A on a qualifying transfer, and the converted shares then follow the resale restrictions.
When could the dates fall?
The prospectus date is the starting point for the day-based triggers. If the final prospectus were dated 13 November 2026, which Yahoo Finance gives as the earliest possible pricing date, the calendar would look like this (VT Markets calculation, for illustration only).
| Trigger | Illustrative date |
|---|---|
| Day 27 | Thursday 10 December 2026 |
| Day 48 | Thursday 31 December 2026 |
| Day 62 | Thursday 14 January 2027 |
| Day 76 | Thursday 28 January 2027 |
| Day 180 (close of trading) | Wednesday 12 May 2027 |
| Day 365 (close of last trading day) | Friday 12 November 2027 |
The earnings-based triggers depend on dates Anthropic has not announced, and the first-quarter 2027 trigger could arrive before day 180 because the filing uses whichever comes first. A later pricing date would move every day-based date by the same number of days.
How does Anthropic’s lockup compare with a typical one?
| Feature | Typical IPO lockup | Anthropic S-1 |
|---|---|---|
| Length | About 180 days for all insiders | 180 days for most holders, up to 365 days for larger holders and co-founders |
| Release structure | Often one date, sometimes with an earnings-based early release | Many staged dates, with 23 unlock dates in the first year according to Business Insider |
| Trigger types | Time-based, sometimes earnings | Both: calendar days and the second full trading day after specific earnings releases |
| Early liquidity | Limited | Up to 10% on day one for non-founder directors, officers and certain employees |
| Founders | Usually the same as other insiders | Up to 29% from day 180 or the first-quarter trigger, the rest after up to a year |
Source: SEC, Wikipedia, Business Insider via Yahoo Finance, and the Anthropic S-1.
Business Insider, in an article published on Yahoo Finance on 27 October 2026, described the schedule as spanning 365 days, far longer than the usual three to six months, and said it contains 23 separate unlock dates against fewer than 10 for SpaceX. It also suggested the staggered structure could cushion post-IPO price declines by releasing shares gradually instead of all at once.
What volatility could the Anthropic lockup create?
A lockup does not cause a price move by itself. It changes how many shares could be sold, and traders watch the dates because supply and sentiment may shift together. Several features of Anthropic’s schedule are worth understanding.
Many small events instead of one large one
With 23 unlock dates reported, no single date is as large as a classic 180-day cliff. The trade-off is that supply is a feature of the market across the whole first year, and there are more dates on which news, earnings and share supply can coincide. Whether this smooths or prolongs volatility is not something the filing can answer.
Earnings and unlocks overlap
Many releases are keyed to earnings, such as the second full trading day after full-year 2026 results or first-quarter 2027 results. That means earnings reactions and extra share supply can arrive together. A strong report could meet a larger pool of sellers, and a weak one could meet the same pool.
Early liquidity from day one
Allowing up to 10% of certain insiders’ locked-up securities to be transferred on the first trading day means some supply could reach the market immediately. It also means employees may have a route to sell for tax or personal reasons, which is a normal reason for insider sales and not necessarily a signal about the company.
Lessons and limits from SpaceX
Business Insider reports that SpaceX shares fell as much as 46% in the months after its IPO before recovering. Reuters notes that SpaceX priced at USD 135, closed its first day at USD 160.95 and closed at USD 147.49 on 23 October 2026. Business Insider also quotes Andy VandenBerg of VDB Wealth as saying that, of the last 30 major tech IPOs, 57% traded up over the first week, and that first-year drawdowns averaged 55%. These are one adviser’s figures and one prior listing, and they do not show what ANT will do.
What is unknown
The share counts and the percentages of the company held by each group are blank in the S-1, so the size of each unlock cannot yet be measured. The price range, the pricing date and the first trading day are also not set. An amended S-1 is expected to add them. The overall AI sector backdrop matters as well, for example how comparable stocks are trading, since Yahoo Finance notes that volatility in comparable stocks can shift IPO timetables.
Lockup, market standoff and 10b5-1 plans: how the terms differ
Three terms appear in coverage of insider selling, and they describe different things.
- Lockup agreement: a contract between a shareholder and the underwriters that restricts sales for a set period. Most of Anthropic’s larger holders are bound this way.
- Market standoff agreement: a similar restriction signed with the company, often by employees and early holders, for the benefit of the underwriters. The S-1 says the underwriters asked for these provisions in connection with the offering.
- Rule 10b5-1 plan: a pre-arranged trading plan that lets an insider schedule future sales. Fortrove Partners notes that officers and directors face a cooling-off period of roughly 90 to 120 days before trades under a new plan can start, and other insiders face 30 days. It also reports that Reuters said Anthropic had considered requiring employees to sell through such plans, with no decision reported, so the final terms should be read from the filing.
The practical difference for traders is visibility. A lockup expiry date is written in the prospectus and can be calendared, while sales under a 10b5-1 plan are scheduled privately and are usually seen only in later disclosures. Neither one says whether an individual holder will sell.
What should traders watch around the Anthropic lockup?
- The final prospectus date: every day-based trigger counts from it.
- The amended S-1: it should show share counts and the price range, so the size of each release can be estimated.
- Earnings dates: the second full trading day after each release is a trigger in the S-1.
- Underwriter releases: early releases or waivers at the representatives’ discretion would be disclosed by the company.
- Volume around unlock dates: Field and Hanka found that average trading volume rose permanently after expiry.
- Broader tech and AI sentiment: other large listings and the market’s appetite for AI shares can affect how unlocks are received.
For the listing timetable itself, the Anthropic IPO date guide covers the reported target of 16 November 2026 and the steps before the first trade.
How can traders approach Anthropic lockup events with CFDs?
A contract for difference (CFD) lets you speculate on the price change of a share without owning it, with the option to go long or short. A CFD on ANT could be available only after the shares list and VT Markets adds the instrument, so check the CFD Shares list at that time.
Before trading around a lockup date, consider the following:
- Event risk: unlock dates and earnings can fall close together, and prices can gap between sessions, so a stop order may fill at a worse price than expected.
- Leverage: it magnifies losses as well as gains, and losses can exceed your deposit.
- Spreads and liquidity: new listings can have wider spreads in the first weeks, especially around news.
- Direction is not implied: a lockup date is not a signal to buy or sell. Prices may rise, fall or barely move.
- Position size and holding costs: CFD positions held overnight can carry financing costs, and the size should be an amount you could afford to lose.
VT Markets does not offer its services in certain countries, so check whether they are available where you live.
Conclusion
An IPO lockup keeps insiders from selling for a set period, and Anthropic’s S-1 turns that into a detailed schedule. Most holders are bound for 180 days or until first-quarter 2027 earnings, larger holders and the co-founders for up to 365 days, and many holders can sell small portions on dozens of dates in between. The filing sets out the dates and percentages, but the share counts and pricing date are still blank. Traders will therefore be watching the amended S-1, the final prospectus date and the earnings calendar, and treating each unlock as a possible source of supply and not as a forecast.
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FAQs
What is an IPO lockup period?
It is a period after an IPO when insiders, such as employees, early investors and executives, are barred from selling their shares. The SEC says most last 180 days. The aim is to prevent a large amount of stock from reaching the market right after listing.
How long is the Anthropic IPO lockup?
Most holders are locked up until the earlier of the second full trading day after first-quarter 2027 results or the 180th day after the prospectus date. Holders of more than 0.5% of fully diluted shares and the seven co-founders are locked up until the earlier of the second full trading day after third-quarter 2027 results or the 365th day.
Can Anthropic insiders sell shares on the first day?
Some can. The S-1 allows non-founder directors, officers and certain current and former employees and consultants to transfer up to 10% of their locked-up securities on the first trading day. Other holders cannot sell until the staged dates, which start on day 27.
What happens to the share price when a lockup expires?
It depends on the stock. The SEC warns that prices may fall before a lockup ends as investors anticipate sales, and a Journal of Finance study found an average three-day abnormal return of -1.5% around expiry. These are averages, and individual stocks can rise, fall or move little.
Can I trade Anthropic with CFDs around lockup dates?
A CFD on ANT could be offered only after the shares are listed and the instrument is available on the platform. CFDs are leveraged products that can lose more than your deposit, and VT Markets does not offer its services in certain countries, so check whether they are available where you live.
Sources
- Anthropic, PBC, Form S-1 registration statement, filed 26 October 2026 (SEC)
- Anthropic, Anthropic files S-1 with the SEC for proposed initial public offering, 26 October 2026
- SEC, Initial Public Offerings, Lockup Agreements
- Business Insider via Yahoo Finance, Let’s try to unpack Anthropic’s wild share-lockup plan, 27 October 2026
- Field and Hanka, The Expiration of IPO Share Lockups, Journal of Finance, April 2001
- Wikipedia, Lock-up period
- Yahoo Finance, When is the Anthropic IPO? The stock could start trading as soon as Nov. 16, 27 October 2026
- Reuters via Investing.com, Factbox: Anthropic’s potential mega IPO joins ranks of world’s biggest listings, 26 October 2026
- Augustus Wealth, Anthropic IPO Lockup and Early Employee Liquidity, 28 October 2026
- Fortrove Partners, Anthropic IPO Lockup Period: Build Your Plan Before the Announcement, updated 28 October 2026
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