NSO Spread at Exercise: Why It's Ordinary Wages, Not Capital Gain

A director of product at a recently-IPO’d enterprise SaaS company exercised 20,000 NSOs in March 2025. Strike $4.60, market price on exercise day $78. Spread: $73.40 per share. Total spread: $1,468,000. Same day, the broker ran a cashless exercise: sold enough shares to cover the strike, commissions, and withholding. The W-2 showed the full $1,468,000 as ordinary compensation. Federal supplemental withholding applied: 22% on the first $1,000,000 and 37% on the remaining $468,000, for total federal supplemental of $393,160. Medicare and California supplemental added on top.

The director had assumed the spread might get some capital gain treatment because he held the underlying options for several years and the value had risen during that time. It did not. Under IRC §83 and §421, an NSO exercise produces ordinary compensation income equal to the spread at the moment of exercise. Holding the option before exercise does not convert the spread to capital gain. The ordinary-rate treatment is the defining tax feature of NSOs and the reason they exist as a separate instrument from ISOs.

The statutory framework

IRC §83 governs the exercise

IRC §83 applies to property transferred in connection with the performance of services. Stock options themselves are not usually “property” under §83 at grant because they typically lack a readily ascertainable fair market value. The exercise of the option, however, transfers shares (which are property) in connection with services.

On exercise, §83(a) provides that the employee recognizes compensation income equal to the excess of the fair market value of the property over the amount paid for it. The “amount paid” for an NSO is the strike price. The fair market value is the exercise-date FMV. The difference is the spread, reported as compensation.

IRC §421 carves out ISOs, not NSOs

IRC §421 provides the ISO exception that defers income recognition on exercise of an ISO that meets the §422 requirements. NSOs do not qualify for the §421 exception. The §83 rule applies in full.

The practical effect: an NSO exercise is treated like receiving cash compensation equal to the spread. The compensation flows through the payroll system. Withholding applies under §3402. Social Security and Medicare taxes apply under §3121 (subject to the SS wage base).

The withholding mechanics

Supplemental rate application

NSO spread is a supplemental wage payment under Treasury Reg §31.3402(g)-1. Supplemental wages paid in a calendar year are subject to withholding at 22% for the first $1 million of aggregate supplemental wages and 37% above.

The $1 million threshold aggregates across all supplemental payments in the year, not just the single NSO exercise. An employee who already received a $500,000 bonus earlier in the year has only $500,000 of 22%-slab capacity remaining. The next $500,000 of NSO spread is at 22%; anything above is at 37%.

NSO spread is wages for FICA purposes under §3121. Medicare (1.45%) applies to the full spread. The additional Medicare tax (0.9%) applies to spread that, combined with other wages, exceeds $200,000 in the year for single filers.

Social Security (6.2% on the employee side) applies up to the wage base ($168,600 for 2025). For senior employees whose other wages have already exceeded the wage base, the NSO spread is not subject to Social Security.

State supplemental

Most states with income tax apply supplemental withholding on NSO spread. California applies 10.23% flat on supplemental wages. New York uses a graduated rate pattern. A handful of states apply their general income tax rates.

The cashless exercise mechanics

Same-day cashless

A cashless exercise is the most common way to handle NSOs. The broker:

Exercises the option, which triggers the company’s obligation to deliver shares.
Sells enough shares at market to cover: strike price, commission, and estimated tax withholding.
Delivers the remaining cash or shares to the employee.

The exercise-and-sell is a single integrated transaction from the employee’s perspective. The W-2 shows the full spread as ordinary compensation. The 1099-B from the broker shows the share sale, with proceeds and basis that should reconcile to near-zero gain or loss.

Cashless hold

A variant is the “cashless hold” where the broker uses the employee’s existing cash or a short-term loan to fund the strike, and the employee ends up with all the shares. The ordinary income is the same. The employee pays the strike from other sources rather than selling shares to cover it.

Cashless hold keeps the full share position but requires cash for strike plus withholding. It is rare except for exercises where the employee wants to hold long-term for capital gain appreciation after the exercise.

Straight cash exercise

The employee writes a check to the company for the strike price and receives all shares into a brokerage account. The company processes the spread as compensation and withholds. The employee pays the strike plus the withholding out of pocket.

Straight cash exercise is typical for small exercises or for exercises done ahead of a planned later sale.

Cost basis after exercise

The cost basis of the shares received at exercise is the exercise-date FMV. This is important for the later sale.

If the exercise spread was $1,468,000 on 20,000 shares ($73.40 per share) at a $78 FMV, the per-share basis going forward is $78. If the shares are sold three months later at $85, the capital gain is $85 - $78 = $7 per share, or $140,000 on 20,000 shares. Short-term capital gain (less than one year from exercise), taxed at ordinary rates.

If held for more than one year from exercise before sale, the same $7 per share is long-term capital gain at 0/15/20% plus NIIT. Some employees exercise and hold the post-exercise shares for long-term treatment on the post-exercise appreciation.

The 1099-B cost-basis trap

The broker’s 1099-B for the exercise-sale transaction may report a cost basis of $0 or only the strike price. Neither is correct. The correct basis is the exercise-date FMV, which equals strike plus spread. The spread was already taxed as compensation on the W-2; the 1099-B basis must add back the spread to avoid double-taxation.

Form 8949 adjustment code B corrects this. Enter the true basis (strike + spread) in the adjustment column. Most broker supplemental statements for equity compensation provide an “adjusted cost basis” column that reflects the proper amount.

The cash-and-hold decision

Exercising NSOs and holding the resulting shares is rarely the right move. The spread is ordinary income regardless of whether the shares are sold or held. Holding exposes the employee to single-stock risk on post-exercise capital, which is the worst-case scenario: you have already paid tax on the full spread, and now you are betting capital on the stock.

Exceptions to the “don’t hold” rule:

The stock is expected to appreciate substantially, and the employee has meaningful conviction.
The employee has capacity to absorb 30%+ drawdowns without financial stress.
Long-term capital gain treatment on post-exercise appreciation is attractive and the employee can hold more than one year.

For most senior employees, the better strategy is exercise-and-sell or cashless same-day, which converts the economic value to cash immediately without taking on additional single-stock risk.

The ordinary-rate comparison to ISOs

The same transaction as an ISO would produce very different tax:

Scenario	Tax treatment	Approximate federal tax
NSO, $1.468M spread	Ordinary income	$520,000+ (37% bracket)
ISO, $1.468M spread, hold for qualifying	AMT preference	$398,000 AMT, recoverable
ISO, $1.468M spread, same-year disqualifying	Ordinary income on actual gain	$520,000+ (same as NSO)

The NSO path is the default “ordinary income” case. The ISO path offers an option (via qualifying holding) to convert to long-term capital gain on the spread, which can save roughly $120,000 on this size exercise if the employee holds long enough.

This is why ISO grants are preferred by early employees at qualifying companies, and why companies often limit ISO grants to the $100,000-per-year threshold and grant excess as NSO.

Frequently asked

Is NSO spread subject to self-employment tax?

No. NSO spread is W-2 wages, not self-employment income. FICA applies, but self-employment tax does not.

Can I elect §83(b) on NSO exercise?

§83(b) applies to property subject to a substantial risk of forfeiture. An exercised vested NSO has no forfeiture risk; there is nothing to elect on. Early exercise of unvested NSOs, if the plan permits, does qualify for 83(b) treatment.

Does the company have to withhold the full marginal rate?

Statutorily, 22% supplemental applies to the first $1M in a calendar year. Companies are required to use this rate. They cannot withhold at the employee’s true marginal rate unless the plan permits elective higher withholding.

What if the broker doesn’t withhold enough?

The employee owes the balance on April 15. Underpayment penalties under §6654 apply if safe harbor thresholds are not met. Quarterly estimated payments can close the gap.

Can NSO spread be deferred?

Only under very limited circumstances that comply with §409A and §3121(v)(2). Most NSOs are not eligible for deferral. The spread is recognized at exercise.

Before your next NSO exercise, model the after-tax outcome at your true marginal rate in the NSO/ISO comparison calculator.