By |Published On: Oct 28, 2026|Categories: Financial Planning, ISOs, NSOs, RSUs|

The Anthropic S-1 is public.

Anthropic filed its S-1 registration statement with the SEC on October 26, 2026. This document officially starts the clock on the IPO process. The Anthropic S-1 discloses the company’s financials, its governance structure, and most importantly for you, the specific terms of the lockup agreement.

This isn’t speculation anymore. These are the actual rules.

Here’s what the filing shows, what it means for your equity, and what you should be doing right now.

What the Anthropic S-1 Discloses

The filing confirms details that have been rumored for months and adds several that weren’t public before.

Listing details: Anthropic plans to list on the Nasdaq under the ticker symbol ANT. The company first submitted a confidential draft registration to the SEC on June 1, 2026. The public filing came on Monday, October 26, 2026.

Scale: As of September 30, 2026, Anthropic had 5,300 employees, up from 940 at the end of 2024. The company’s revenue run-rate has surpassed $47 billion. The filing also discloses significant compute commitments that represent the capital intensity of the business model.

Governance: Dario Amodei, Daniela Amodei, and Anthropic’s five other co-founders will hold 50.1% of total voting power through the Founder LLC, Class F common stock that retains operational control with the founding team after the IPO.

Timing: Based on the Anthropic S-1 and typical IPO timelines, a trading start in mid-November 2026 is possible, though not confirmed.

The Anthropic S-1 Lockup Structure

Most IPO lockups are simple: insiders are locked for 180 days after trading begins, then everything opens. Anthropic’s structure is deliberately different and it’s built around earnings release dates rather than a fixed calendar.

The Anthropic S-1 filing describes four distinct lockup tiers depending on your role and share count. Understanding which tier applies to you is the first question to answer, because the timeline and planning calculus are different for each.

Tier 1: Non-founder directors, officers, and most employees

The full lockup for this group expires at the earlier of the second trading day after Q1 2027 earnings or Day 180, with two early windows:

  • Day 1 (first trading day): Up to 10% of your locked shares can be sold
  • 2nd trading day after FY26 earnings (~Feb–March 2027): An additional 35% unlocks
  • Remainder: At the earlier of Q1 2027 earnings or Day 180 (~May 2027)

This is the schedule that applies to most Anthropic employees. Three windows, a full lockup endpoint of roughly May 2027.

Tier 2: Certain stockholders (non-employee investors below the 0.5% threshold)

This Anthropic S-1 tier also expires at the earlier of Q1 2027 earnings or Day 180. But the early release schedule is more granular, starting at Day 27 and running through the FY26 earnings window:

Window% of Locked Shares ReleasedCumulative
Days 27 & 48 after IPO6% each12%
Days 62 & 76 after IPO7% each26%
2nd trading day after FY26 earnings12.5%~38.5%
13, 27, 41, 55, 69 days after FY26 earnings9.5% each~86%
Q1 2027 earnings or Day 180Remainder100%

This group gets earlier access to small amounts starting at Day 27, but the same ultimate endpoint as Tier 1.

Tier 3: Large holders (>0.5% of fully diluted shares, non-founders)

Stockholders holding more than 0.5% of fully diluted shares are on the most extended schedule. It’s a full lockup that runs until the earlier of Q3 2027 earnings or Day 365, with roughly 20 early windows spread across more than a year:

Window% of Locked Shares ReleasedCumulative
Days 27 & 48 after IPO1.8% each3.6%
Days 62 & 76 after IPO2.1% each7.8%
2nd trading day after FY26 earnings3.75%~11.5%
13, 27, 41, 55, 69 days after FY26 earnings2.85% each~26%
Q1 2027 earnings or Day 1804.2%~30%
34, 48, 62, 76 days after Q1 2027 earnings5.6% each~52%
2nd trading day after Q2 2027 earnings7%~59%
27, 41, 55, 69, 83 days after Q2 2027 earnings6.3% each~91%
Q3 2027 earnings or Day 365Remainder100%

Under the Anthropic S-1, the tranches drip from Day 27 through late 2027. If you held more than 0.5% of fully diluted shares as of approximately seven days before the prospectus date, this is your schedule, not Tier 1.

Tier 4: Founders

Founders are on the simplest but most restrictive structure. The full lockup runs until the earlier of Q3 2027 earnings or Day 365. There is one early provision: founders may transfer up to 29% of their locked shares beginning at the earlier of the second trading day after Q1 2027 earnings or Day 180. That is the only exception until the full lockup ends.

Why the Anthropic S-1 lockup structure matters

For most employees (Tier 1), the planning is three windows. For large holders (Tier 3), it’s closer to 20. The tax implications scale accordingly. Each window is a potential sale event, and a sale in 2026 (Window 1), 2027 (FY26 earnings window), or later carries different federal holding period treatment. Getting the sequencing wrong doesn’t just cost money once. It compounds.

It also means that tax events are spread across multiple calendar years. A sale in Window 1 (2026) can be taxed differently than a sale in Window 3 (2027). California residents face the same ordinary income rate regardless of holding period. But federal long-term capital gains treatment kicks in after 12 months from the day you acquired each specific lot, which makes the tax lot selection decision as important as the timing decision.

What the Anthropic S-1 Means for Each Equity Type

RSUs

RSUs issued under a double-trigger structure vest when both conditions are satisfied: your service period and a liquidity event (the IPO). If your RSUs have been sitting in pre-IPO limbo waiting for a liquidity event, the Anthropic S-1 IPO filing is the first step toward that second trigger being satisfied.

Once RSUs vest, you have ordinary income on the fair market value of the shares at vesting, regardless of whether you can sell them during the lockup. Anthropic is expected to withhold shares to cover minimum tax obligations, but the net shares you receive are still taxable as W-2 income in the year of vesting.

For California residents, the state income tax rate on that income applies at ordinary rates. There is no lower rate for capital gains at the state level. See the California tax guide for the full implications.

ISOs

ISOs don’t create income at exercise, but they do create an AMT preference item. If you’ve been holding unexercised ISOs waiting for the IPO, the Anthropic S-1 filing changes your math. You now have a likely IPO date against which to plan your exercise timing, spread, and AMT exposure.

If trading starts mid-November and you exercise ISOs before December 31, 2026, the AMT spread is a 2026 tax event. If you wait and exercise after January 1, it becomes a 2027 event. The difference in your tax bill can be material.

For a framework on exercise timing relative to IPO, see Should Anthropic Employees Exercise ISOs Before the IPO?

NSOs

NSOs create ordinary income on exercise equal to the spread between exercise price and fair market value at the time of exercise, not at sale. The IPO establishes a public market price, which becomes the fair market value reference point.

If you’re holding unvested or unexercised NSOs, the Anthropic S-1 filing is the moment to revisit your exercise strategy. See Anthropic NSO Exercise Strategy for the full analysis.

Stock options generally — the 10b5-1 question

The S-1 filing begins the “quiet period,” a window during which you are generally prohibited from trading based on material non-public information. Until the IPO closes and trading begins, most employees should assume they are in possession of MNPI.

If you were planning to establish a 10b5-1 trading plan before the IPO, you need to understand the quiet period constraints carefully. See Anthropic 10b5-1 Trading Plan for how this affects plan setup timing.

The Anthropic S-1 Urgency Calendar

The Anthropic S-1 creates a specific sequence of decisions, each with a deadline. Here’s the timeline as it stands today.

Now through IPO pricing (likely mid-November 2026):

  • Review your equity award details: type, quantity, vesting status, cost basis
  • Model your tax exposure for each equity type
  • Decide whether to exercise ISOs before year-end (a 2026 vs. 2027 AMT question)
  • If you haven’t already: consult an estate planning attorney about pre-IPO gifting strategies (see Estate Planning Before the IPO)
  • If you’re charitably inclined: a donor-advised fund contribution before IPO is one of the highest-leverage tax moves available (see Donor-Advised Fund strategy)

At IPO – Window 1 (Day 1, up to 10% of locked shares):

  • Decide whether to use your first unlock allocation
  • Understand that selling on Day 1 is a short-term capital gain if shares were acquired at vesting and taxed as ordinary income
  • Holding through Day 1 carries to future windows

After full-year 2026 results (Window 2, ~Feb–March 2027):

  • Another 35% eligible; total up to 45% cumulatively eligible
  • If shares have appreciated since IPO, selling here may mean the gain is still short-term depending on your specific lot dates
  • Coordinate with your 10b5-1 plan if you set one up

After Q1 2027 results or 180 days (Window 3, ~April–May 2027):

  • Remaining shares eligible for most employees
  • This is the first point where long-term capital gains treatment is possible for shares acquired at or near IPO
  • If you acquired them at vesting with the IPO as the trigger, the holding period runs from the vesting date

What to Do Now

The Anthropic S-1 filing is the moment most people think they need to act. It isn’t. It’s the moment you need to plan, so you’re ready to act at the right time.

Locate your equity award agreements. Your grant agreements spell out the specific vesting conditions, exercise prices, and expiration dates for every award you hold. Before you can plan, you need to know exactly what you have.

Understand your lockup tier. The Anthropic S-1 describes four distinct groups: standard employees, certain stockholders, large holders (>0.5% of fully diluted shares), and founders. Each are on a different schedule. The large-holder schedule has roughly 20 unlock windows tied to earnings dates. The founder schedule is simpler but more restrictive. Confirming which tier you’re in is the first question to answer, because the entire planning timeline flows from it.

Model your tax before you sell anything. The sequence in which you sell — which lots, in which windows — determines how much you keep. See Which Anthropic Shares Should You Sell First? for the full tax lot selection framework.

Think about what’s leaving Anthropic before the IPO, not just after. If you’ve recently left or are considering leaving, the equity treatment at departure is different from still being employed at IPO. See Leaving Anthropic Before the IPO for the specifics.

The Bottom Line

The Anthropic S-1 changes the question from “when will the IPO happen?” to “what do I do with the equity I’m about to be able to sell?”

Those are different questions with different answers. The first was about waiting. The second is about sequencing. Get the order of decisions right so that a liquidity event you’ve worked toward for years doesn’t produce a tax bill you didn’t see coming.

The staggered lockup structure gives you multiple chances to get this right. It also means multiple chances to make a costly decision under pressure. The employees who come out ahead won’t be the ones who reacted fastest at Window 1. They’ll be the ones who planned before Window 1 opened.

For a full overview of how all of this fits together, start with the Anthropic IPO Employee Equity Guide.

Schedule a free consultation with Fortrove Partners →

This article is for informational purposes only and does not constitute tax, legal, or financial advice. Equity compensation decisions involve complex tax considerations specific to your situation. Work with a qualified tax professional and a CERTIFIED FINANCIAL PLANNER® professional before acting.

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