You built something that genuinely changed the world. Now you’re sitting on a grant agreement with an exercise price from 2021 that reads like a typo compared to Anthropic’s current $965 billion pre-IPO valuation. Your Anthropic ISO exercise decision may be the most consequential financial move you make this decade. Also: the IRS noticed.
For most Anthropic employees holding ISOs from early grant vintages, the right move is to exercise before the IPO, in tranches, up to your AMT crossover point. The Anthropic ISO exercise decision is consequential enough – and irreversible enough – that it deserves more than a Slack thread and a hunch. This guide gives you the framework: the concepts, the math, the scenarios, and a checklist to work through before you act.
No article can give you a personal answer. But you’ll leave here understanding exactly what you’re deciding, and why the clock is moving faster than the company announcements make it feel.
What Makes an ISO Different – and Why Timing Your Anthropic ISO Exercise Matters So Much
Let’s orient quickly, because the mechanics determine the strategy.
An Incentive Stock Option gives you the right to buy Anthropic shares at your exercise price – the fixed price set at the time of grant, based on the 409A valuation when your options were issued. If you received grants in 2021 or 2022, that exercise price might have been a few dollars per share. Anthropic’s pre-IPO valuation is now approximately $965 billion. The mathematical gap between those two numbers is called the spread. For early employees, it may be extraordinarily large.
When you exercise ISOs, two things happen simultaneously.
First, you start your holding period clocks. Hold shares for at least one year after exercise and two years after the grant date, and your eventual sale gains qualify for long-term capital gains rates – currently 20% federally. The alternative is ordinary income treatment at 37%. On a seven- or eight-figure gain, that difference runs into hundreds of thousands of dollars. The holding period clock doesn’t start ticking until you actually exercise, so waiting doesn’t preserve optionality – it costs it.
Second, the spread on ISO exercise creates Alternative Minimum Tax (AMT) exposure. This is where the complexity begins, and where most employees get into trouble.
The AMT Problem: What the ISO Spread Does to Your Tax Bill
This is the part that surprises even sophisticated employees: when you exercise ISOs, the spread doesn’t show up as ordinary income for regular tax purposes. That’s the ISO advantage. However, it does appear as income under the Alternative Minimum Tax system – a parallel tax framework designed by the IRS to ensure that high earners pay at least a minimum amount, regardless of deductions and preferences.
You calculate your taxes twice: once under the regular system, once under AMT rules. Then you pay whichever is higher.
For 2026, the AMT exemption is $90,100 for single filers and $140,200 for married couples filing jointly. These exemptions phase out once your Alternative Minimum Taxable Income (AMTI) exceeds $500,000 for single filers and $1,000,000 for married filers. The AMT rate is 26% on the first $244,500 of AMTI above the exemption, and 28% on anything above that.
When the spread on your ISO exercises pushes your AMTI high enough that AMT exceeds your regular tax, the difference becomes your AMT liability – payable on April 15 of the following year, regardless of whether you can sell any shares to fund it.
You could exercise ISOs in October 2026 at a near-trillion-dollar valuation, trigger a substantial AMT liability, and then find yourself locked out of selling a single share until April 2027. Your tax bill would be due months before the shares could pay for it. This scenario isn’t theoretical. It happened to early employees at multiple tech companies whose stocks crashed post-IPO – people who owed taxes on paper gains the market never validated.
Their AMT credit was recoverable via Form 8801, technically, but recovering a large AMT credit can take years of sufficient tax liability to absorb. That’s cold comfort in April.
The AMT Crossover: The Number You Must Calculate Before Acting on Your ISOs
The AMT crossover is the point at which your AMT liability exactly equals your regular tax liability. Below the crossover, you owe your regular tax and nothing extra. Above it, every additional dollar of ISO spread triggers an incremental AMT bill.
Here’s a concrete illustration – not your numbers, but a framework for understanding the concept:
Imagine an Anthropic employee with a $350,000 salary and a $300,000 bonus, filing as single. Their regular federal income tax runs roughly $225,000. They hold ISOs with an exercise price of $8 per share, and the current 409A fair market value is approximately $180 per share – a spread of $172 per share.
- Exercise 5,000 ISOs: The spread adds $860,000 to their AMTI, for a total of roughly $1.61 million. The AMT exemption phases out almost entirely. Their AMT liability calculates to approximately $200,000. They owe the additional ~$200,000 difference as an AMT bill, in cash, in April.
- Exercise 1,000 ISOs: The spread adds $172,000, bringing AMTI to roughly $822,000. The resulting AMT approaches $10,000 – still above regular tax, but the AMT exposure is dramatically smaller.
The goal of the tranche strategy is to identify the exercise quantity at which AMT equals regular tax – and stay at or below it for 2026. Your specific crossover depends on your income, deductions, filing status, and spread. A tax advisor with equity compensation experience can model this in a single session. Doing it yourself with a spreadsheet is possible, but the error tolerance here is very low. Given the stakes, the planning fee is the best investment you’ll make this year.
Why an Early Anthropic ISO Exercise Is Advantageous – and What Could Go Wrong
Two specific benefits come from exercising ISOs now, before the IPO.
First, you start your holding period clock at a lower valuation. If the IPO prices Anthropic at $1 trillion or higher – not an unreasonable projection – shares you exercise today have a lower cost basis than shares exercised at IPO pricing. The spread locks in at the time of exercise. That means lower AMT exposure and more of your eventual gain taxed at long-term capital gains rates rather than ordinary income rates.
Second, you preserve more optionality. Once the S-1 is filed and the SEC review is underway, pre-clearance requirements and blackout restrictions may limit when you can act on your grants. The pre-IPO planning window you’re in right now is the widest and cleanest you’ll have. After the roadshow starts, calendars fill, compliance requirements multiply, and the administrative machinery of going public consumes everyone’s attention – including yours.
The Downside Scenarios You Need to Know
If the IPO is delayed significantly, or if Anthropic’s valuation at listing is lower than the current pre-IPO figure, you’ll have paid AMT based on a spread the market ultimately didn’t validate. In an extreme scenario – think early-2000s tech wreck, not a garden-variety correction – that becomes an AMT disaster. As noted above, the credit is recoverable via Form 8801, but recovery depends on having sufficient future tax liability, and the timeline is unpredictable.
The mitigation for both risks is the same: don’t exercise beyond your AMT crossover, and don’t exercise any amount you’d be uncomfortable holding through a market correction. Those two constraints together are your margin of safety.
Three Scenarios: How the Timing Choice Plays Out
To make the comparison concrete, here’s how the same hypothetical Anthropic employee fares under three approaches.
Scenario A: Exercise in tranches now, before IPO
The employee exercises up to their AMT crossover in 2026 and again in 2027 if needed. They manage a modest, planned AMT bill rather than a catastrophic one. Holding period clocks start at a lower valuation. Shares sold after one year post-exercise and two years post-grant qualify for long-term capital gains treatment. The cash outlay spreads across tax years.
Scenario B: Wait and exercise at IPO
Double-trigger RSUs vest and ISOs are exercised at or near IPO pricing – both generating income in the same tax year. RSU vesting hits as ordinary income; ISO spread hits AMTI. The combined AMT exposure may be severe, and the liquidity to pay it is locked behind a 180-day lockup. This is the setup for an April tax bill with no accessible shares to fund it.
Scenario C: Wait and exercise post-lockup
The employee can now sell shares to fund the tax bill, but has missed the long-term capital gains holding period on ISO shares at a lower basis. Depending on stock price movement during lockup, the bill may still be calculated on a valuation they couldn’t capture.
Scenario A is generally best for employees with significant early-vintage ISOs and the cash to fund exercises at a manageable tax cost. Scenario B can be appropriate for employees with small spreads or very recent grants, where the timing advantage is minimal.
California Makes Everything Harder (Sorry)
If you’re based in San Francisco, you face a California state AMT on top of the federal one. The state imposes its own alternative minimum tax at 7%, and – and California does offer an AMT credit — but it works differently than the federal version. The federal AMT credit can offset your regular federal tax in future years.
The challenge is often not whether the credit will be available, but when it can be used. For taxpayers who generate a large California AMT liability from an ISO exercise, there can be a significant cash-flow mismatch: the state tax may be due in April, while the shares remain unsold because of holding requirements, blackout periods, or other liquidity constraints.
That detail alone is worth a full conversation with a California-specific tax advisor before you exercise a single share. In many cases, it changes the math substantially.
Your Anthropic ISO Exercise Checklist
Before acting on your incentive stock options, work through these five questions carefully.
1. What is my exercise price and how many ISOs do I hold?
Pull your grant agreements from Carta or your employee portal. Document exercise price, grant date, expiration date, and vesting status for each grant separately – you likely have multiple grants at different prices and vintage years.
2. What is Anthropic’s current 409A fair market value?
This is your spread denominator. The 409A is set by an independent valuation firm and should be available through your equity portal or HR. It changes periodically – confirm you’re using the most current figure before modeling anything.
3. What is my AMT crossover in 2026?
This calculation requires modeling your full tax picture: salary, bonus, other income sources, deductions, and filing status. A tax advisor or financial planner with equity compensation experience can run this in a single session. For fee-only fiduciary advisors, lets make a plan is a reliable starting point.
4. Do I have the cash to exercise and cover any resulting AMT?
The cash outlay is twofold: the exercise price itself (shares × exercise price) and any AMT bill due the following April. Both need to be covered by liquid funds – not by shares you can’t sell yet. Don’t exercise more than you can fund in cash.
5. Am I confident enough in the October 2026 IPO timeline?
If the Anthropic IPO slips a year, your shares won’t be tradeable as early as planned. That’s not necessarily a reason to hold off on exercising – but it should factor into how much capital you’re willing to commit and how you think about the holding period.
Frequently Asked Questions
Should Anthropic employees exercise ISOs before the IPO?
For most employees holding ISOs with early grant prices and large spreads, yes – exercising in tranches before the IPO, up to the AMT crossover point, is generally advantageous. It starts the long-term capital gains holding period at a lower valuation and limits AMT exposure. The right answer depends on your individual circumstances.
What is the AMT crossover point?
The AMT crossover is the number of ISOs you can exercise in a given year before your Alternative Minimum Tax liability exceeds your regular tax. Below this threshold, you owe no additional AMT. Above it, each additional dollar of ISO spread triggers incremental AMT. Your crossover is specific to your income, deductions, and filing status – it requires modeling, not estimation.
What are the 2026 AMT exemption amounts?
For 2026, the AMT exemption is $90,100 for single filers and $140,200 for married filing jointly. Exemptions phase out at $500,000 AMTI for single filers and $1,000,000 for married filers. The AMT rate is 26% on the first $244,500 of AMTI above the exemption, and 28% on amounts above that threshold.
What happens if I exercise ISOs and the Anthropic IPO is delayed?
You’ve started your holding period clocks earlier than necessary, but you haven’t made an irreversible error – assuming you exercised within your AMT crossover limit and have the liquidity to hold. The primary risk: if Anthropic’s valuation at listing is significantly lower than today’s pre-IPO figure, the AMT you paid was calculated on a spread the market never validated.
Can I exercise ISOs after the Anthropic IPO?
Yes – but you’ll likely be exercising into a higher share price, which increases your AMT exposure. Additionally, you’ll be subject to blackout windows and trading policy restrictions as a public company employee. The pre-IPO window is generally the most favorable environment for ISO exercise planning.
What’s the difference between exercising an ISO and an NSO?
When you exercise an ISO, the spread is not taxed as ordinary income for regular tax purposes – it flows into AMTI for AMT calculation only. When you exercise an NSO, the spread is taxed as ordinary income immediately, regardless of AMT. ISOs carry a potentially more favorable tax outcome but require careful timing. NSOs are simpler but more immediately expensive.
What is the ISO exercise window after leaving Anthropic?
Most ISOs convert to NSOs or expire if not exercised within 90 days of your departure. Some plans offer extended windows for long-tenure employees – check your grant agreement. If you’re considering leaving before the October IPO, treat the 90-day exercise window as a hard deadline and model your tax exposure before your last day.
Do I need a financial advisor to handle my Anthropic ISO exercise?
For employees with significant ISO grants and large spreads, yes. Federal AMT, California state taxes, the lockup period, and the IPO timeline interact in ways that are genuinely hard to navigate without professional guidance. Look for a fee-only fiduciary advisor with specific experience in pre-IPO equity compensation.
The Window Is Open Now
The planning window you’re in right now – between the S-1 filing and the start of the roadshow – is the best environment you’ll have for these decisions. Once the IPO process accelerates, blackout periods expand, your calendar disappears, and the administrative machinery of going public consumes everyone’s attention.
The time to model your AMT crossover, pull your grant agreements, and talk to an advisor is now. Before September. Before the roadshow. Now.
Schedule a free consultation with Fortrove Partners →
Related Reading: The Filing That Changes Everything: Your Anthropic IPO Employee Equity Survival Guide