How NSOs are taxed: the bargain element and everything after

When does an NSO actually get taxed? The day you exercise, not the day you sell. That one fact runs the entire NSO tax story, and the thing being taxed has a name: the bargain element. Almost every NSO tax surprise traces back to misreading that single moment, so it is worth burning in.

This is the complete tax picture for non-qualified stock options, start to finish. First the bargain element itself and why it is ordinary income. Then the payroll surtaxes that ride on top, the withholding gap that quietly leaves high earners short, and exactly how to close it before it becomes a penalty. Then the part that plays out years later: your real cost basis and the broker error that taxes you twice, the capital gain after exercise and what holding actually buys you, the net investment income tax, and one clean piece of good news, that an NSO never drags you into the AMT the way an ISO does. Read it in order the first time. Come back to any section when you are about to act.

22%

Supplemental withholding

37%

On wages over $1M

0.9%

Additional Medicare

3.8%

Net investment income tax

The bargain element is the whole tax story

The bargain element is the spread. It is the stock’s fair market value on the day you exercise, minus the strike price you paid. Exercise 1,000 options with a $10 strike when the shares are worth $60, and the bargain element is $50,000. The IRS treats that $50,000 as ordinary income, the same bucket as your salary and your cash bonus. It lands in the year you exercise, whether or not you sell a single share.

Why ordinary income and not a capital gain? The logic is simple once you see it. You got the right to buy stock cheap as part of your pay. The moment you use that right, you have received something of value for your work, so it is compensation. Compensation is ordinary income. The capital gains clock does not even start until after exercise, when the shares are yours.

$50,000 spread

You keep ~$29,000

Tax + withholding ~$21,000

Illustrative split. Your real share depends on your bracket, the payroll surtaxes, and your state. The point is that the spread is taxed like salary the year you exercise.

The payroll tax on top

Because the spread is wages, it is not only hit with income tax. Social Security and Medicare apply too, up to the usual limits, exactly as they would on a bonus. People lump the surtaxes together and panic, but keep them apart and the picture is clean: one set rides on the compensation, another rides later on the investment gain.

The surtax has a wrinkle worth knowing. Your employer must start withholding the 0.9% once your wages pass $200,000, regardless of how you file. Your own liability threshold depends on filing status: $200,000 single, $250,000 2026 married filing jointly, $125,000 2026 married filing separately. So you can end up owing a little more, or getting a little back, when you reconcile on Form 8959. The withholding is a blunt instrument; the return is where it squares up.

The lever you control: which year

Here is the second-order point most people miss. The tax is not fixed by the size of your grant. It is fixed by how much spread you turn into income in a single tax year. Stack a huge exercise into one year and you can shove the spread up through your brackets, paying the top rate on the last dollars. Spread the same exercises across two or three years and more of it can stay in lower brackets.

10%

$12,400

12%

$50,400

22%

$105,700

24%

$201,775

32%

$256,225

35%

$640,600

37%

over

Step height tracks the rate. The label under each step is the top of that bracket, and only the dollars that land inside a bracket are taxed at its rate.

That makes the timing of an NSO exercise a real planning decision, not a formality. The cleanest versions are to exercise in a low-income year on purpose, or to spread exercises across tax years so each chunk fits inside your bracket headroom.

Withholding usually falls short

Does your company withhold enough when you exercise? Usually not, and the shortfall is by design. The spread gets withheld at the flat supplemental wage rate, and for most people holding meaningful equity, that rate sits below the rate the income is actually taxed at. The gap is yours to cover.

The flat supplemental rate is one number for everyone. Your marginal rate is not. If your income puts you above that flat rate, every dollar of spread is being withheld at less than it will eventually be taxed. The difference does not vanish. It shows up as a balance due when you file, and possibly an underpayment penalty on top.

Closing the gap before it becomes a penalty

It is the same trap RSU holders hit with their flat withholding, and the fix is the same: true it up before the IRS does it for you with a penalty attached.

Your real cost basis (and the trap that taxes you twice)

After you exercise and pay tax on the spread, what is your basis in the shares? The strike price plus the spread you already paid ordinary tax on. That second part is the whole game, because brokers routinely leave it out, and when they do, you pay tax twice on the same money.

Two pieces, added together. The first is the strike, the cash you paid to exercise. The second is the bargain element, which already hit your W-2 as ordinary income. Adding it to your basis is what stops it from being taxed a second time. Exercise 1,000 options at a $10 strike when the stock is $60: you paid $10,000 in strike, the $50,000 spread was taxed as wages, and your basis is the full $60,000, which is just $60 a share, the value on exercise day.

The trap is mechanical, and it is almost universal. Your brokerage knows what you paid in strike. It usually does not know about the spread that ran through your paycheck. So the 1099-B it sends often lists your basis as only the strike, or sometimes $0.

What if I sell at the same price I exercised at?

Then your gain is roughly zero, because your basis is the exercise-day price. But if the 1099-B shows only the strike, that same sale looks like a large gain. A break-even sale can generate a fake tax bill purely from a basis error, which is why you check it even when you did not make a dime.

Capital gains on the shares after exercise

Once the ordinary income is behind you, the shares become ordinary stock, and a totally separate tax applies from there: capital gains, on whatever the price does next. This is the easy half.

Sell later for more than your basis, and the difference is a capital gain. Sell for less, and it is a capital loss. The spread you already paid ordinary tax on is not taxed again, because it is baked into your basis. How long you hold past exercise decides the rate.

Hold the shares more than a year from the exercise date, and the gain is long-term, taxed at the lower long-term rates. Sell within a year of exercise, and the gain is short-term, taxed at your ordinary income rate, the same as your salary, with no discount.

Single

0%

15%

20%

$49,450 $545,500

Married filing jointly

0%

15%

20%

$98,900 $613,700

The rate steps up at each dollar threshold. Long-term gains stack on top of your ordinary income to decide which band they fall in. Band widths are illustrative, not to scale.

Does holding NSO shares for a year save much tax?

It only helps on the gain after exercise, not on the spread you already paid full ordinary tax on. If the stock barely moved since exercise, there is almost nothing to discount, so holding buys you little and exposes you to single-stock risk the whole time. The hold-versus-sell call is a risk decision dressed up as a tax one.

The net investment income tax

In a big year, the long-term rate is not the only number in play. The net investment income tax is 3.8% 2026, and it does not touch the spread at all. Wages are not investment income, so the compensation piece of your NSO is out of its reach.

What the NIIT can reach is the capital gain after exercise. Once you hold the shares and sell them higher, that gain is investment income. For 2026 the 3.8% applies to the lesser of your net investment income or the amount your modified adjusted gross income runs over $250,000 2026 married filing jointly, or $200,000 2026 single. Here is the second-order sting: the spread inflates your income for the year, which can push your MAGI over the NIIT line, so the wage event helps trigger a tax on the investment gain even though the wage itself is exempt. A high earner selling appreciated NSO shares can face the 20% long-term rate plus the 3.8% surtax, so “long-term” does not always mean cheap.

So a same-day exercise and sale avoids the NIIT?

Largely, yes. If you exercise and sell immediately, there is little or no post-exercise gain, because your basis is the exercise-day price. No gain, almost nothing for the NIIT to bite. The spread is still wages and still in play for the Medicare surtax. Selling same-day kills the investment tax, not the compensation tax.

Does holding longer change which surtax applies?

It changes the rate on the gain, not the surtax math. The 3.8% NIIT applies whether the gain is short-term or long-term. Holding past a year gets you the lower long-term rate on the gain itself, but the NIIT rides on top either way once your income clears the threshold.

One piece of good news: NSOs do not trigger the AMT

Do NSOs trigger the alternative minimum tax? No. And that one word is the main reason some people would rather hold NSOs than ISOs.

The AMT is a second tax calculation that adds back certain items the regular system ignores, then makes you pay whichever total is higher. The ISO bargain element is one of those added-back items: exercise and hold an ISO and the spread is invisible to regular tax but fully counted by the AMT, so you can owe real cash tax on a paper gain you never sold. That is the ISO AMT trap. An NSO works in the open. The spread is ordinary income right when you exercise, taxed inside the regular system, so there is no hidden preference for the AMT to drag back in.

The honest footnote, so I do not overclaim: a large NSO exercise raises your regular taxable income, and that higher income is the starting point the AMT calculation builds on, so a big year can affect where you land relative to the AMT in general. That is different from the ISO problem, where the exercise itself creates a special AMT-only add-back. With an NSO, there is no NSO-specific AMT item. The income is just ordinary income, and you can take the AMT off your worry list as a special concern.

What this means for you

The bargain element is the entire NSO tax in one phrase: the spread at exercise, taxed as ordinary income, in the year you exercise. Everything else is logistics. Plan the year so the spread does not crest your brackets. Set aside the gap the flat withholding leaves behind, and pay it quarterly if it is large. Guard your real basis, the exercise-day value, so a broker error does not tax you twice. Then watch the capital gain and the 3.8% surtax in a high-income sale year, and leave the AMT off the list entirely.

Simple rules, a handful of numbers, and one decision that genuinely moves money: which year you recognize the spread. If your exercise is large enough to move your bracket or clear the surtax thresholds, that is worth a conversation before you click the button.