ISOs, NSOs, and RSUs: The Tax Rules Nobody Explains Clearly

Henry Supinski, ChFC® · 4 min read · July 2026

Equity compensation comes in a few different flavors, and each one is taxed differently. Mixing them up is one of the most expensive mistakes a tech employee can make.

RSUs: Taxed the Moment They Vest

Restricted stock units are taxed as ordinary income when they vest, based on the share price that day. There's no election to defer it and no way to avoid it. Whatever you do afterward (hold or sell) only affects the capital gain or loss on top of that already-taxed amount.

NSOs: Taxed at Exercise, Not at Grant

Non-qualified stock options generate ordinary income at exercise, equal to the difference between the exercise price and the fair market value that day. That income shows up on your W-2 and is subject to withholding. Any further gain after exercise is a capital gain, taxed based on how long you hold the shares afterward.

ISOs: The One With the AMT Trap

Incentive stock options can qualify for favorable tax treatment (long-term capital gains on the entire gain) but only if you meet strict holding period rules and don't trigger the Alternative Minimum Tax along the way. Exercising ISOs and holding the shares can create an AMT bill even though you haven't sold anything and haven't received any cash. This is the single most common expensive surprise in equity compensation.

The Practical Takeaway

• RSUs: ordinary income at vest, no choice involved.
• NSOs: ordinary income at exercise, plus capital gains after that.
• ISOs: potential AMT at exercise, potential long-term capital gains treatment if holding rules are met, real risk if the stock drops after you've exercised and paid AMT on paper gains.

If your company has granted you more than one type, the right move (exercise, hold, or sell) is different for each one, and they interact with your overall tax bracket in ways that are easy to get wrong without modeling it out first.

The Second Trap: Cost Basis Reporting

There is a quieter mistake that shows up at filing time. When RSUs vest or NSOs are exercised, the income lands on your W-2, and your basis in the shares steps up to the value used for that income. But brokers often report only what you paid out of pocket, which for RSUs is zero. If you or your preparer copy that 1099-B basis without adjusting it, you pay tax on the same dollars twice: once as wages, then again as a phantom capital gain. Anyone selling shares that came from equity compensation should check the basis line before filing. Every year. No exceptions.

A Hypothetical Side by Side

Take a hypothetical employee holding all three grant types at a company trading at $50 per share.

Her 1,000 RSUs vest this year. That is $50,000 of ordinary income at vest, no decision required, and her basis in those shares is $50.

She exercises 1,000 NSOs with a $10 strike. The $40 spread creates $40,000 of ordinary income on her W-2 the day she exercises, and her basis becomes $50. Whatever happens after that is capital gain or loss.

She also exercises 1,000 ISOs with a $10 strike and holds the shares. Nothing hits her W-2. But the $40,000 bargain element counts as income for AMT purposes, which can create a real tax bill this year on shares she has not sold and cash she has not received. If the stock then drops to $20, she may have paid AMT on paper value that no longer exists. Every number here is invented. That last scenario is not. It has burned people in every tech downturn I have watched.

How We Approach It

I held equity comp at SAP with my own money, so I know how abstract these rules feel until a vest date or an expiring exercise window makes them concrete. Our process is the same for every equity client. First, inventory every grant by type, strike, vest date, and expiration. Second, model the ordinary income, AMT exposure, and capital gains treatment for each realistic path. Third, sequence the decisions across tax years instead of letting expiration dates make them for you. The full framework lives on our equity compensation planning page, and it connects to everything else we do in planning and investment management.

Questions We Hear

What are the ISO holding rules for capital gains treatment?

To get long-term capital gains treatment on the full spread, you generally must hold the shares at least two years from the grant date and at least one year from the exercise date. Sell earlier and it becomes a disqualifying disposition, which converts some or all of the gain into ordinary income. A disqualifying disposition is sometimes still the right move. It should be a choice, not an accident.

Is there any way to avoid tax when RSUs vest?

For standard public-company RSUs, no. Vesting is a taxable event. Planning shifts to what you can control: the withholding gap, the hold-or-sell decision after vest, and how a heavy vest year interacts with your other income. Anyone promising a way around tax at vest is describing something other than standard RSUs.

How do I know if exercising ISOs will trigger AMT?

You model it. AMT is a parallel tax calculation, and the bargain element on exercised-and-held ISOs is one of its main triggers. The outcome depends on the size of the spread, your other income, and your deductions. Exercising in smaller batches across years, or exercising when the spread is still thin, are common ways to manage the exposure. Run the projection before you exercise, not at filing time.

Which type of equity is best?

You rarely get to choose, and the honest answer depends on what the stock does. RSUs hold value even in a flat market. Options can be worth far more in a rising market and nothing in a falling one. The more useful question is what to do with the mix you actually have. That is a sequencing and tax question, not a preference question.