Your company just announced its IPO roadshow. You're sitting on Incentive Stock Options (ISOs) that could be worth serious money—but only if you make the right move in the next few months.
Exercise now and you may reduce taxes in some scenarios. Or you might trigger a massive tax bill for stock that could become worthless. Wait too long and you could lose the tax benefits entirely.
This can be one of the most financially significant decisions for many startup employees. The window is narrow, the math is complex, and the consequences of getting it wrong can be costly and may be difficult to reverse. In our liquidity event framework, this falls squarely in the Assessment and Strategy Design phases—and it's where most people need the most help. In our Pre-IPO Planning Checklist, we introduced the ISO exercise question as one of the critical decisions requiring modeling. Now we're going deep: what's actually at stake, what variables matter, and why this decision can't be made in isolation.
What Makes ISOs Different?
ISOs offer a unique tax advantage that no other equity compensation provides: if you play by the rules, your entire gain can be taxed at long-term capital gains rates instead of ordinary income rates. In certain circumstances, favorable ISO treatment can result in long-term capital gains tax treatment rather than ordinary income. Actual rates and outcomes depend on individual facts and current law.
But that "if" is doing a lot of work.
To get the favorable tax treatment, you need to satisfy multiple requirements:
- Hold the stock for at least two years from the grant date
- Hold for at least one year from the exercise date
- Remain employed when you exercise (in most cases)
- Not sell within the disqualifying disposition period
- Navigate the Alternative Minimum Tax (AMT) system
Miss any of these requirements and your ISOs become taxed exactly like ordinary stock options—meaning you lose the entire advantage.
The AMT Trap: Why Exercising ISOs Isn't Free
Here's what catches most people off guard: even though you don't owe ordinary income tax when you exercise ISOs, you may owe Alternative Minimum Tax.
When you exercise ISOs, the spread between your strike price and the fair market value becomes an AMT "preference item." This is phantom income—you haven't sold anything, you haven't received cash, but the IRS treats it as income for AMT purposes.
Example: You exercise ISOs with a $1 strike price when the 409A valuation is $10 per share. That $9 spread? It's added to your AMT income, even though you're just holding paper stock.
The AMT rate is 28% for higher earners, and it kicks in when your preference items push you above certain thresholds. For 2025, the AMT exemption starts phasing out at $626,350 for single filers and $1,252,700 for married filing jointly.
Translation: if you exercise a large ISO position before an IPO, you could owe significant AMT—payable in April of the following year—for stock you can't yet sell.
The Brutal Scenario: Paying Taxes on Worthless Stock
- This downside scenario can occur, including in periods of market volatility and post-IPO price declines.You exercise ISOs when your company is valued at $10/share, paying AMT on a $9 spread
- The company goes public at $8/share
- The lockup expires and the stock drops to $5/share
- You sell at $5, which means your actual gain is only $4 per share ($5 sale price minus $1 strike price)
- But you paid AMT calculated on a $9 phantom gain
You've paid taxes on income that never materialized. The AMT credit you'll eventually receive doesn't fully compensate you for paying taxes on a $9 gain when you only made $4.
This isn't hypothetical. This happened to employees at dozens of companies during the 2000 dot-com crash and again after several high-profile IPOs in recent years.
The QSBS Consideration: Another Layer of Complexity
If your company qualifies for Qualified Small Business Stock (QSBS) treatment under Section 1202, exercising ISOs early could give you access to the QSBS exclusion—potentially allowing you to exclude up to $10 million in gains from federal taxes (and in some states, state taxes as well).
But QSBS has strict requirements:
- You must hold the stock for five years from the date of exercise
- The company must be a C-corp with less than $50 million in assets when you exercised
- You need proof of your 83(b) election filing (if applicable) and exercise date
- The stock must have been acquired in exchange for services, not purchase
Exercising ISOs specifically to capture QSBS treatment means locking in an even longer holding period—and accepting even more risk that the stock price moves against you.
As we covered in the Pre-IPO Planning Checklist, documenting your QSBS qualification requires proof of your 83(b) filing and exercise date—paperwork that many people don't have when they need it five years later.
Should You Exercise? The Variables That Matter
This decision comes down to several interconnected factors:
How confident are you in the company's trajectory? If you believe the IPO price will be significantly higher than the current 409A valuation, exercising early locks in a lower AMT basis. If you're wrong, you've paid taxes on phantom gains.
Can you afford the AMT bill? You'll need cash to pay AMT in April following the year you exercise. If you're exercising a meaningful position, this amount could be substantial. Most people don't have that kind of liquidity readily available.
How much AMT space do you have? Your existing income, deductions, and other AMT items affect how much ISO spread you can absorb before triggering AMT. This requires modeling your specific tax situation.
What's your time horizon? To get long-term capital gains treatment, you need to hold for one year from exercise and two years from grant. To get QSBS treatment, you need to hold for five years from exercise. Can you lock up this capital for that long?
What's the IPO timing? If the IPO happens soon after you exercise, you'll hit the lockup period without satisfying the one-year holding requirement. Selling during the lockup expiration becomes a disqualifying disposition, converting your ISOs to ordinary income.
Some companies offer tender offers before the IPO, which can provide liquidity without the ISO exercise decision. We've written a separate guide on tender offer decisions if you're facing that option.
What happens if you leave the company? Most ISO agreements give you only 90 days to exercise after you leave. If you haven't exercised yet and you leave before the IPO, you're forced into a decision with even less information.
How does this connect to your post-IPO diversification strategy? Your ISO exercise decision directly affects your ability to diversify after the IPO. If you exercise pre-IPO, you're locked in for at least a year (and potentially five years for QSBS). Your diversification strategy post-IPO—which we'll cover in our next post—depends entirely on the decisions you make now.
The Strategy: Partial Exercise and Creating "AMT Space"
For most people, the answer isn't "exercise everything" or "exercise nothing." It's a calibrated partial exercise strategy.
One approach: exercise enough ISOs to fill your available "AMT space"—the amount of ISO spread you can absorb before triggering significant AMT. Then, manage your other income and deductions to create more AMT capacity.
Some people strategically sell other stock positions at a gain to increase their regular tax liability, which increases the amount of ISO spread they can absorb before hitting AMT. Others time the exercise across multiple tax years to spread the AMT impact.
But this level of coordination requires modeling:
- Your current year tax projection
- Your AMT exemption and phaseout thresholds
- The ISO spread at current 409A valuation
- Potential IPO pricing and timing
- Post-IPO holding period scenarios
- QSBS qualification analysis
This isn't back-of-the-envelope math. One miscalculation and you've either left tax savings on the table or triggered a massive unexpected tax bill.
What Most People Get Wrong
Mistake #1: Waiting until the IPO is announced Once the IPO is imminent, the 409A valuation jumps closer to the expected IPO price. Your window to exercise at a low valuation—and lock in a smaller AMT hit—has closed.
Mistake #2: Exercising everything at once Going all-in maximizes your AMT bill and your risk. If the stock price drops post-IPO, you've paid the maximum possible tax on phantom gains.
Mistake #3: Ignoring the AMT credit You will eventually get credit for AMT paid, but it only offsets regular tax in future years when you're not in AMT. Many people pay AMT for years before they can use the credit, creating a significant cash flow problem.
Mistake #4: Not stress-testing the downside Everyone models the upside (stock goes up 10x!). Almost no one models the downside (stock drops post-IPO and I've paid significant AMT on phantom gains).
Mistake #5: Trying to optimize this in isolation Your ISO decision affects your cash flow, your portfolio concentration, your tax situation for multiple years, and your estate planning. Optimizing one variable while ignoring the others leads to suboptimal outcomes.
Why This Requires Coordinated Planning
Here's what makes this decision so complex: you're not just making a tax decision. You're making an investment decision, a cash flow decision, a risk management decision, and a multi-year tax planning decision—all at once.
The optimal answer for someone with substantial savings and low confidence in the company is completely different from someone with limited liquid assets and high confidence in the company.
The math changes based on:
- Your state tax situation (California AMT works differently than federal)
- Your other income sources
- Your diversification needs
- Your timeline for needing liquidity
- Your risk tolerance
- Whether you're planning to leave the company
Many professionals specialize in either tax or investment strategy. Because ISO decisions can affect both, some individuals benefit from a coordinated planning approach.
How We Help
This is why Brickley Wealth Management combines CPA services and financial advisory under one roof.
When you're facing an ISO exercise decision, you need:
- Tax modeling to project your AMT liability under different exercise scenarios
- Investment analysis to evaluate concentration risk and portfolio impact
- Cash flow planning to ensure you can afford the AMT bill
- Scenario analysis to stress-test downside outcomes
- QSBS qualification review if applicable
- Multi-year tax strategy to optimize across your entire timeline
We model all of this together—because your ISO decision isn't just about 2025 taxes. It's about your financial position for the next five to ten years.
Whether we work with your existing CPA or provide both services directly, we work to align tax considerations and investment strategy based on your goals and circumstances.
Facing an ISO exercise decision? Because outcomes depend on your specific situation, consider getting personalized advice from qualified professionals.
Next in this series: How to Sell Company Stock After an IPO—because the decisions you make now directly impact your diversification strategy post-IPO.