Published May 19, 2026 · Last updated: May 2026 · Tax Planning Services
RSUs, ISOs, and Incentive Equity: The Tax Complexities Every Recipient Should Understand
- RSUs vest as ordinary income at fair market value on the vest date — not when sold. Most NJ/NY employers under-withhold significantly at the 22% supplemental rate.
- The cost basis trap: brokerages often report $0 or incorrect RSU/ESPP cost basis on Form 1099-B. Filing without adjusting Form 8949 results in double taxation on income already on your W-2.
- ISOs can create an AMT preference item at exercise which may trigger AMT depending on the taxpayer’s full income, deductions, and other AMT items. Not regular income tax. The 2026 OBBBA phaseout reset ($500K single / $1M MFJ at 50% rate) makes 2026 ISO exercises more AMT-sensitive than 2025 on the same spread.
- Federal supplemental withholding does not cover NJ/NY state tax, and state supplemental withholding may still fall short of the taxpayer’s actual marginal state liability. Bergen County residents with large vesting events routinely owe $15,000–$40,000 in additional state tax at filing.
- New Jersey conforms to QSBS exclusion starting January 1, 2026. NJ startup employees with qualifying QSBS gain can now exclude it from both federal and NJ state tax.
A Bergen County software engineer walked into our office in March carrying a W-2 he did not recognize. He had RSUs, and he had ISOs. His salary looked right. But there was $180,000 in Box 1 he had never seen before. It was not a raise. It was three years of RSUs vesting in a single calendar year, all hitting ordinary income at once, all withheld at the 22% federal supplemental rate. His actual combined NJ and federal marginal rate was closer to 45%. He owed $40,000 more than had been withheld.
This is not a cautionary tale from some rare edge case. It is the most common equity compensation problem we see in our practice.
Equity compensation is a genuine wealth-building tool. RSUs from a public company, ISOs at a fast-growing startup, an ESPP at a firm with a 15% purchase discount, QSBS shares in a pre-IPO company that qualifies under Section 1202, these are real financial opportunities. But every one of them creates a tax event that arrives before most recipients expect it, in a form they did not anticipate, at a cost their employer's HR team did not explain.
This guide covers the tax mechanics of every major type of incentive equity. For each type, I've noted who it applies to and what the actual cost is, not the textbook version, the version we see on real returns filed by NJ and NY clients every year.
RSUs: The Tax That Hits Whether You Sell or Not
Restricted Stock Units are taxed as ordinary income on the date they vest. Not the date you sell. Not the date you receive cash. The date the shares land in your account. The fair market value of the shares on that vest date is added to your W-2 as compensation income, right alongside your salary, as if you had been paid a bonus in stock rather than cash.
Here is what that means in practice. If 1,000 RSUs vest on a Tuesday when your company's stock is trading at $85, you have $85,000 in new ordinary income on that Tuesday. If your employer's stock drops to $60 by Friday and you sell then, you still owe income tax on $85,000, plus you now have a $25,000 capital loss that can only offset capital gains or $3,000 of ordinary income per year. The tax was locked in at vest.
The 22% withholding problem. Most employers handle RSU taxes through a sell-to-cover process: at vest, they automatically sell enough shares to cover the withholding. That withholding is calculated at the IRS supplemental wage rate of 22%, or 37% if your total supplemental wages for the year exceed $1 million. For a Bergen County resident in the 32% federal bracket, also subject to NJ Gross Income Tax at up to 10.75% and potentially NY tax at up to 10.9%, the 22% federal withholding covers roughly half of the actual tax owed. The rest is due in April. This is why our engineer owed $40,000 he had not planned for. The fix is estimated quarterly tax payments made throughout the year.
The cost basis trap. After RSUs vest and you eventually sell the shares, your brokerage will send you a Form 1099-B reporting the proceeds. The problem: many brokerages report a cost basis of $0 or report only the original grant-date value, not the fair market value at vest that you already paid income tax on. If you plug those brokerage numbers into your return without adjustment, you report the full sale proceeds as a capital gain. You pay tax on income you already paid income tax on. This is double taxation on the same dollars, and it is the most common cause of IRS CP2000 notices related to equity compensation. The correct cost basis for RSU shares is the FMV at vest, the same number that appeared on your W-2. You adjust this on Form 8949. If you are not sure whether your cost basis has been correctly reported, verify this with your CPA before your return is filed.
Post-vest capital gains. Once you own the shares after vesting, subsequent appreciation is taxed as capital gains. Hold more than one year from the vest date for long-term capital gains rates, a maximum 20% federal rate for most high-income taxpayers. Hold less than one year and any gain is taxed at ordinary income rates. The holding period begins at vest, not at grant.
Restricted Stock vs. RSUs. These are different instruments. Restricted Stock requires the employee to purchase the shares, often at a nominal price, and allows the Section 83(b) election. RSUs are granted without purchase and do not allow the 83(b) election. This distinction matters enormously at startups, where founders and early employees typically receive Restricted Stock, not RSUs, and where the 83(b) election can make a substantial difference in eventual tax outcomes.
ISOs: The Favorable Treatment That Comes With a Hidden Bill
Have RSUs vesting or ISOs to exercise this year? The NJ/NY tax picture is more complex than your employer's HR team explained. Our licensed CPAs model the full scenario before you act.
Book a free equity compensation consultation →ISOs are the most tax-advantaged form of stock option available to employees. When everything goes according to plan, an ISO holder can convert what would have been ordinary income into long-term capital gains, a difference of roughly 20 percentage points in federal rate for high-income taxpayers. That is a real and substantial benefit. It is also conditional on meeting specific holding requirements and navigating one of the most commonly misunderstood tax provisions in the code.
Qualifying disposition requirements. To achieve long-term capital gains treatment on an ISO, you must hold the shares for at least two years from the grant date and at least one year from the exercise date. Both conditions must be met. Miss either requirement and you have a disqualifying disposition. In that case, the bargain element is generally treated as ordinary compensation income, subject to a key limitation: if the shares are sold below their exercise-date fair market value, ordinary income generally cannot exceed the actual gain on sale. Any remaining gain or loss is handled under capital gain/loss rules.
What happens at exercise. When you exercise an ISO, you pay the exercise price and receive company shares. You owe no regular federal income tax on exercise. But the spread, the difference between the exercise price and the fair market value of the shares on the day you exercise, is an AMT preference item. It gets added to your Alternative Minimum Tax income (AMTI) for the year of exercise, even though you have recognized no cash gain and paid no regular income tax.
The 2026 AMT problem. The One Big Beautiful Bill Act permanently restructured AMT phaseout rules effective January 2026. Prior to 2026, the AMT exemption phaseout did not begin until AMTI reached approximately $1.25 million for joint filers and $626,000 for single filers. The phaseout rate was 25%. Starting in 2026, the OBBBA reset the phaseout thresholds to $1,000,000 for joint filers and $500,000 for single filers, and doubled the phaseout rate to 50%. The 2026 AMT exemption amounts are $90,100 for single filers and $140,200 for joint filers (IRS Rev. Proc. 2025-32). Those exemptions are eliminated faster as income rises above the new lower thresholds.
Consider a single NJ/NY filer earning $300,000 in salary who exercises ISOs with a $500,000 spread. Total AMTI: approximately $800,000. They are $300,000 above the $500,000 phaseout threshold. At the 50% phaseout rate, their $90,100 exemption is reduced by $150,000, eliminating it entirely. They owe AMT on the full $800,000. Run the same exercise in 2025 and the result is materially different. The same spread, the same salary, a substantially lower AMT bill under the old phaseout rules. Modeling ISO exercises using 2025 assumptions for 2026 exercises is one of the costliest planning errors we expect to see this year. The numbers changed.
The $100,000 annual ISO limit. ISOs that become first exercisable in a calendar year with aggregate FMV exceeding $100,000 automatically convert the excess to Non-Qualified Stock Options. This is missed when multiple ISO tranches vest simultaneously, which happens regularly at startups where four-year grants concentrate in a single year for early employees. Plan around this.
The AMT credit carryforward. AMT paid on ISO exercise generates a credit on Form 8801 that can offset future regular tax in years when your regular tax exceeds your AMT. For ISO holders who exercised in prior years and built AMT credit carryforwards, those credits provide real relief in future years. Track them.
The 83(b) election and early exercise. If your company allows early exercise of ISOs before vesting, file the Section 83(b) election within 30 days of exercise using IRS Form 15620. It accelerates income recognition to when the spread is small, starts your capital gains holding period immediately, and if done early enough in a company's lifecycle, can minimize both regular and AMT exposure. The 30-day window is absolute. There is no extension. There is no cure for a missed election.
NSOs: The Simpler Option With No Favorable Treatment
NSOs are taxed as ordinary income at exercise on the spread between your exercise price and the fair market value of the stock at exercise. That income is reported on your W-2 (employees) or Form 1099-NEC (non-employees) in the year of exercise. You do not get to defer recognition until you sell.
NSOs are also subject to FICA payroll tax at exercise, Social Security and Medicare, on top of income tax. ISOs are not subject to FICA at exercise. The 0.9% Additional Medicare Tax applies to exercise income above $200,000 for single filers. Post-exercise, hold more than one year from exercise to qualify for long-term capital gains rates.
The multi-state NSO sourcing problem. For NJ/NY metro employees who have changed states or worked remotely across states during the NSO vesting period, state tax on NSO income is sourced to where services were performed during the grant-to-exercise period, not where you live when you exercise. If an NSO was granted in New York, you moved to New Jersey two years later, and you exercised in Florida, all three states may assert a portion of the gain based on workdays in each state during the grant-to-exercise period. Moving to a no-income-tax state does not eliminate the prior-state claim on NSO income that was earned there.
ESPPs: The Discount That Creates a Tax Surprise
Section 423 qualified ESPPs allow eligible employees to purchase company stock at a discount, typically 15% off market price. For an employee contributing the maximum to a plan with a 15% discount, the math produces a guaranteed 17.6% return before any market appreciation, making it one of the highest-returning employer benefits available when properly managed.
Qualifying disposition. Hold shares at least two years from the offering date and one year from the purchase date. The discount portion of your gain is ordinary income when you sell. The remaining appreciation is long-term capital gains.
Disqualifying disposition. Sell before either holding period is met. The full spread at purchase, the FMV on purchase date minus your discounted purchase price, is ordinary income at sale, reported on your W-2. The remaining gain is capital.
The cost basis trap. Many brokerages report ESPP cost basis using only the discounted purchase price, not the FMV. Taxpayers who use the 1099-B without adjusting for the W-2 ordinary income portion over-report capital gains and pay double tax on the same income. It is the same error as RSU cost basis, in a different form. Adjust Form 8949 before filing.
OBBBA and AMT in 2026: Why This Year Requires a New Model
The OBBBA permanently reset AMT phaseout thresholds to $500,000 single / $1,000,000 MFJ starting January 2026, and doubled the phaseout rate from 25% to 50%. AMT exemptions phase out twice as fast, starting at a lower income level. More ISO holders will owe AMT in 2026 on exercises they could have completed with minimal AMT in 2025.
Source: IRS Rev. Proc. 2025-32; Tax Foundation 2026 Tax Brackets analysis; confirmed by multiple CPA sources.
The 2026 AMT exemption amounts are $90,100 for single filers and $140,200 for married joint filers, up modestly from 2025 due to inflation. But those exemptions phase out starting at $500,000 for single filers and $1,000,000 for joint filers, at a 50% phaseout rate. For every $2 of AMTI above the threshold, you lose $1 of exemption. A single filer with $680,000 in AMTI, just $180,000 above the $500,000 threshold, loses $90,000 of their exemption, leaving them with only $100 remaining.
The AMT credit carryforward remains intact. AMT paid in 2026 generates Form 8801 credits that offset future regular tax in years when regular tax exceeds AMT. For clients with accumulated AMT credit carryforwards from prior years, 2026 may not be the year to aggressively exercise. The credit bank may not be needed for several years, and adding more AMT liability extends the horizon before it is fully utilized.
The rule: before exercising any ISO tranche in 2026, model the full dual-tax comparison, regular tax liability versus AMT liability, using 2026 threshold and rate assumptions. The exercise window that was safe in 2025 is narrower in 2026. Confirm your model with a licensed CPA before acting.
The NJ/NY State Tax Dimension That National Guides Miss
Every national equity compensation guide covers federal mechanics adequately. None of them tell you what happens if you work in NJ or NY.
The withholding gap. When RSUs vest, your employer withholds federal tax at the 22% supplemental rate and state tax at a flat supplemental rate, typically not at your actual NJ or NY marginal rate. NJ's Gross Income Tax reaches meaningful rates well below the top bracket. NY's top rate reaches 10.9% on the highest incomes, with 9.65% applying above $1,077,550 for single filers. NYC residents add up to 3.876% in city income tax on top of state. Bergen County residents with large RSU vesting events frequently owe $15,000 to $40,000 in additional NJ and NY tax at filing not covered by employer withholding. The fix is estimated quarterly payments made throughout the year.
The NJ RSU workday allocation formula. New Jersey allocates RSU income to NJ based on where work was performed during the period from grant to vest. The formula: NJ taxable RSU income equals total RSU income multiplied by NJ workdays divided by total workdays during the grant-to-vest period. Moving to Florida before the final vest does not eliminate NJ's claim on the NJ-allocated portion. NJ takes the position that those RSUs were earned during the period in which NJ services were performed.
New York's convenience of employer rule. If you work remotely in New Jersey for a New York-based employer and your employer has not specifically required you to work from New Jersey, New York treats your remote work as if it were performed in New York. Your entire compensation, including RSU vest income and ISO exercise gains, is considered New York-source income. NJ may give you a credit for taxes paid to New York, but only up to NJ's own rate. For NJ residents working for NY employers where NY rates exceed NJ rates on the relevant income, double taxation is a genuine risk. NJ adopted its own reciprocal convenience of employer rule effective January 1, 2023 (NJ P.L. 2023 c.125), applying the same logic in reverse for NY residents working remotely for NJ employers.
The NJ QSBS opportunity, new in 2026. This is the planning angle most NJ startup employees have never been told about, because it did not exist until this year. New Jersey has historically not conformed to the federal Qualified Small Business Stock exclusion under Section 1202. NJ residents who qualified for the federal QSBS exclusion still owed full NJ Gross Income Tax on those same gains.
That changed. New Jersey enacted Bill A4455/S4503, signed by Governor Murphy on June 30, 2025, bringing NJ into conformity with IRC Section 1202 for tax years beginning January 1, 2026. NJ startup employees whose QSBS gains are excluded at the federal level now have those same gains excluded for NJ GIT purposes. Combined with the OBBBA's enhancements for stock issued after July 4, 2025, including a raised gross asset cap of $75 million, a raised per-taxpayer exclusion of $15 million, and a new tiered holding period of 50% exclusion at three years, 75% at four years, and 100% at five years, NJ startup employees holding qualifying QSBS now have a planning window that did not exist before 2026.
The 83(b) election matters here too. The QSBS holding period begins when you acquire the stock. For Restricted Stock with a timely 83(b) election filed within 30 days of grant or early exercise, the holding period starts at acquisition, not at vesting. Filing the 83(b) correctly can accelerate the QSBS clock by years.
The 5 Most Expensive Equity Compensation Mistakes We See
Not adjusting Form 8949 for RSU and ESPP cost basis
The brokerage sends a 1099-B with low or zero cost basis. The taxpayer enters it as-is. The IRS receives a report of capital gains on income already taxed as ordinary compensation on the W-2. IRS CP2000 notices on equity compensation are overwhelmingly caused by this single error. Fix: confirm cost basis on every equity sale equals the FMV at vest or exercise, not the grant price or zero.
Exercising ISOs in 2026 without modeling AMT under OBBBA rules
The phaseout thresholds dropped to $500K/$1M. The phaseout rate doubled to 50%. An exercise window that produced no AMT in 2025 may produce five or six figures of AMT in 2026 on the same spread. Run the full dual-tax model before exercising. Use 2026 rules, not last year's.
Assuming employer withholding at vest is adequate
It almost never is for NJ and NY residents with large vesting events. The 22% supplemental rate is a starting point. Calculate the gap between what will be withheld and what you will actually owe, then make estimated quarterly payments. Do not wait until April to discover the shortfall.
Ignoring multi-state workday allocation on RSUs and options
Remote workers who have moved states, employees commuting between NJ and NY, and former NJ or NY residents who moved before shares vested all face state tax exposure tied to prior-state workday records. The source state does not forget your RSU grant just because you moved. Know the NJ allocation formula. Work with a CPA who handles multi-state equity sourcing.
Missing the 83(b) election deadline
Thirty days from grant or early exercise. No extensions. No exceptions. No retroactive cure. IRS Form 15620 is the required form. For founders and early startup employees where the 83(b) election can convert a future ordinary income event into a QSBS-eligible capital gains event starting from day one, missing this deadline is one of the most expensive and irreversible tax errors we see. Set the reminder the day the grant is signed.
Model Your Equity Tax Before the Event, Not After
RSUs vesting, ISOs to exercise, or startup equity approaching liquidity, the time to model the tax is before the event, not in April after the withholding gap has already been locked in. Our NY- and NJ-licensed CPAs handle equity compensation returns across all instruments and multi-state scenarios.
Book a free equity compensation consultation →Also read: NJ BAIT Election Guide 2026 — the entity-level tax election that reduces federal tax for NJ pass-through business owners.
