Employees at a company going through an acquisition or IPO — trying to understand what happens to their ISOs vs NSOs in a liquidity event, and the AMT risk that comes with it.
What Happens to Your ISOs vs. NSOs in an Acquisition or IPO?
A liquidity event changes the math for both grant types — but ISOs carry a specific risk most employees don't see coming.
Understand your specific tax exposure before shares get cashed out or start trading.
An acquisition or IPO is the moment your equity stops being theoretical — and the ISO/NSO distinction determines how much of that value the IRS takes before you see it.
The AMT Bomb: Why ISOs Get Risky at High Valuations
If you exercise ISOs and hold the shares through an acquisition or IPO, the spread between your strike price and the (now much higher) fair market value can trigger a large Alternative Minimum Tax bill — sometimes before you've sold a single share to cover it. This is the single most common "surprise tax bill" story among startup employees.
Why NSOs Are Simpler (But Taxed Sooner)
NSOs sidestep the AMT issue entirely because the exercise spread is already taxed as ordinary income when you exercise. In a liquidity event, that means less surprise — but also less opportunity for the lower long-term capital gains rate that a well-timed ISO exercise can capture.
- Exercising ISOs right before an IPO without a plan to cover AMT is the classic mistake
- A cashless exercise at acquisition typically avoids the AMT problem entirely
- NSO tax is already "baked in" by the time your liquidity event happens
Frequently Asked Questions
Will I owe AMT if my company gets acquired and I hold ISOs?
You may, if you exercised your ISOs and held the shares rather than selling immediately at the acquisition. The AMT is triggered by the exercise spread, not the acquisition itself, so timing your exercise relative to the deal matters.
- Model your AMT exposure before exercising, not after the deal closes
- Selling shares in the same transaction as exercise often avoids AMT
- A tax advisor familiar with liquidity events is worth the cost here
Do NSOs get taxed differently than ISOs when a company goes public?
Not at the IPO itself — but if you already exercised NSOs earlier, that tax was due at exercise, not at the IPO. Any further gain from the IPO price increase is taxed as capital gains when you eventually sell.
- NSO tax timing doesn't change because of the IPO
- Only post-exercise gains get capital-gains treatment
- Plan your sale timing around lock-up periods, not just tax rates
The Lovie Advantage
By the time an acquisition or IPO is on the table, founders and employees both need clean, current numbers — not a reconstruction project. Internal Link: Lovie Cap Table Management keeps grant types, exercise dates, and valuations current from formation onward, so modeling a liquidity event doesn't start with a spreadsheet archaeology exercise.
If you're leaving the company for reasons unrelated to an acquisition, the exercise-window rules are different — see Internal Link: How Long You Have to Exercise After Leaving. For background on the specific tax mechanics, the National Venture Capital Association's model legal documents offers useful context on how these terms are typically drafted.
Model Your Liquidity Event
Understand your specific tax exposure before shares get cashed out or start trading. Start Free with Lovie