You Have Stock Options. Do You Know Which Kind?

Most tech employees have never read their stock option agreement.

That's not a criticism. Option agreements are dense, written by lawyers for lawyers, and buried somewhere in a DocuSign folder from your first week at the company. But inside that document is a detail that will significantly affect how much of your equity you actually keep, and most people don't find out what it says until they're already in the middle of a major decision.

The detail is this: what type of stock options do you have?

The two most common are Incentive Stock Options (ISOs) and Non-Qualified Stock Options (NSOs, sometimes called NQSOs). They look similar on the surface. Both give you the right to purchase company stock at a fixed price. Both can be worth significant money if your company grows. But they are taxed in completely different ways, and understanding the difference can be worth tens of thousands of dollars, sometimes more.

The short version

ISOs get preferential tax treatment under the federal tax code. If you meet certain conditions, the profit from ISOs is taxed at long-term capital gains rates rather than ordinary income rates, a meaningful difference when you're in the 32–35% federal bracket.

NSOs don't get that treatment. When you exercise an NSO, the spread, meaning the difference between your strike price and the current fair market value, is taxed as ordinary income, immediately, at your full marginal rate. California treats it the same way.

That distinction matters enormously when you're deciding whether and when to exercise.

How to tell which one you have

The fastest way to find out is to look at your option agreement or your equity platform. Most companies use Carta, Shareworks, or a similar tool. Your grant will be labeled either ISO or NSO, or sometimes NQSO.

A few rules of thumb worth knowing:

ISOs can only be granted to employees. If you're a contractor, advisor, or board member, your options are NSOs by default. The tax code doesn't allow ISOs for anyone who isn't a W-2 employee.

There's an annual ISO limit. Only the first $100,000 in options, measured by the grant date fair market value, that vest in any given year can qualify as ISOs. Anything above that automatically converts to NSO treatment. If you have a large grant with a heavy vesting schedule, some of your options may be ISOs and some may be NSOs without it being obvious.

Companies choose. Startups generally try to grant ISOs to employees because the favorable tax treatment is a valuable part of the compensation package. But nothing requires them to, and some companies, particularly at later stages or in certain circumstances, grant NSOs instead.

If you're not sure what you have, find out now. Don't wait until you're ninety days from your last day at the company.

How ISOs are taxed, and where it gets complicated

The ISO tax advantage comes with conditions. To qualify for long-term capital gains treatment on the full spread, you need to meet two holding period requirements: hold the shares for at least two years from the grant date, and at least one year from the exercise date. If you sell before meeting both requirements, it becomes a disqualifying disposition and the spread is taxed as ordinary income, exactly like an NSO.

So far, straightforward. Here's where it gets complicated.

When you exercise ISOs, even if you hold the shares and don't sell anything, the spread is counted as income for purposes of the Alternative Minimum Tax. The AMT is a parallel tax system designed to ensure high earners pay a minimum level of tax regardless of deductions. For most W-2 employees it doesn't apply. For startup employees exercising ISOs with significant appreciation, it can create a large tax liability, sometimes six figures, on income that exists only on paper.

This is the ISO trap that catches people off guard. You exercise options, you owe taxes, but you haven't sold anything. The cash has to come from somewhere else.

The AMT risk is real, it's significant, and it's the primary reason ISO exercise decisions should never be made without first modeling the tax consequences. The right amount to exercise in a given year, if any, depends on your income, your other deductions, the spread on your options, and how much AMT exposure you're willing to take on given the uncertainty about the company's future.

How NSOs are taxed: simpler, but more expensive

NSOs don't have the AMT complexity, but they don't have the upside either.

When you exercise an NSO, the spread is taxed as ordinary income in the year of exercise. Your employer will withhold taxes, and the income shows up on your W-2. From that point forward, your cost basis in the shares is the fair market value on the day you exercised, so any future appreciation is taxed as capital gains, either short-term or long-term depending on how long you hold.

The simplicity is real. There's no holding period requirement to get capital gains treatment on future appreciation, and there's no AMT exposure on exercise. But you're paying ordinary income tax on the full spread at exercise, at your marginal rate, which at Bay Area tech income levels is significant.

One planning opportunity with NSOs is timing. If you can control when you exercise, for example in a year when your income is lower or when the spread is smaller, you can reduce the tax hit. This requires looking ahead, which is exactly the kind of planning most people don't do until it's too late.

The 90-day window

Whether you have ISOs or NSOs, there's one number every option holder needs to know: 90 days.

When you leave a company, voluntarily or otherwise, most option agreements give you 90 days to exercise your vested options. After that window closes, the options expire worthless. It doesn't matter how much they're worth on paper. If you don't exercise within the window, you lose them.

This catches people by surprise more often than it should. Someone leaves a company after four years, assumes their equity will be there when the company eventually goes public, and discovers months later that their options expired. The money is gone.

A smaller number of companies, mostly those that have made explicit commitments to employee-friendly equity policies, offer extended post-termination exercise windows of five or ten years. But that's the exception, not the rule. If you're considering leaving your company, your option agreement is one of the first things worth reviewing.

A practical framework

Here's how to think about your options clearly, regardless of which type you have:

Know what you have. ISO or NSO, strike price, vesting schedule, expiration date. All of it. This information is in your equity platform and your option agreement.

Understand the tax treatment before you exercise. For ISOs, model your AMT exposure. For NSOs, understand the ordinary income hit. Neither calculation is complicated with help, but both are expensive to learn about after the fact.

Don't let perfect be the enemy of good. The most common mistake isn't making the wrong decision about options. It's making no decision, letting options expire, missing exercise windows, or holding illiquid stock without a plan because the tax situation feels too complicated to navigate.

Know your window. If you're thinking about leaving your company, your vesting schedule and exercise window are part of the financial picture, not an afterthought.

The bottom line

ISOs and NSOs are not interchangeable. The tax treatment is different, the planning considerations are different, and the mistakes are different. The first step is simply knowing which one you have, and then making sure the decisions you make about them are intentional ones.

If you have stock options and you're not sure where to start, that's exactly the kind of thing worth talking through before a major decision forces your hand.