For employees with equity compensation from public-company or startup grants — including RSUs, stock options, or ESPP shares.
Equity compensation is one of the areas where the gap between what employees understand and what the tax code actually does is widest. A restricted stock unit vests and feels like a paycheck. A stock option is exercised and feels like an investment decision. An ESPP purchase closes and feels like a discount buy.
In each case, a tax event has just occurred — sometimes a large one — and the timing, the type of income it creates, and the decisions available before and after that moment matter significantly. This article explains how each type of equity compensation is taxed, where the common misunderstandings sit, and what planning considerations apply regardless of which type you have.
Restricted Stock Units (RSUs)
RSUs are the most common form of equity compensation at public companies. When RSUs vest, the fair market value of the shares on the vesting date is recognized as ordinary income, reported on your W-2, and subject to federal and state income tax, Social Security tax, and Medicare tax.
There is no decision to make at vesting the way there is with options. The income is recognized automatically when the shares are delivered. The employer typically withholds taxes, but the withholding rate on supplemental income — commonly 22% at the federal level — may fall well below your actual marginal rate if total income for the year is substantial. That gap accumulates across each vesting event and often becomes visible only at filing time.
After vesting, the shares have a cost basis equal to the value reported as income. Any subsequent gain is a capital gain. Hold the shares for more than one year after vesting and the gain qualifies for long-term capital gains treatment. Sell within one year and the gain is short-term, taxed at ordinary income rates.
Illustrative: An employee with $180,000 in base salary receives a $60,000 RSU vest mid-year.
• Employer withholds at 22% federal supplemental rate: $13,200 withheld on the vest.
• Actual marginal federal rate on the combined $240,000 total income: 32%.
• Approximate withholding shortfall on the RSU vest alone: roughly $6,000.
• If two more vesting events occur during the year, the shortfall compounds.
Key assumption: state withholding gap is separate and additional. Actual results depend on full-year income, filing status, and deductions.
Incentive Stock Options (ISOs)
ISOs carry the most favorable potential tax treatment and the most planning complexity. Exercising an ISO does not trigger ordinary income tax in the year of exercise. No income is reported on your W-2 at exercise.
What does happen is an alternative minimum tax adjustment. The spread between the exercise price and the fair market value at exercise — the bargain element — is added to AMT income. For employees with significant ISO exercises, this can produce a meaningful AMT liability even though no regular income was recognized.
If shares are held for at least two years from the grant date and at least one year from the exercise date — a qualifying disposition — the entire gain from exercise price to sale price is taxed as long-term capital gain. Selling before either holding period is met triggers a disqualifying disposition, converting the gain to ordinary income and eliminating the favorable treatment.
One important clarification: some companies permit employees to exercise options before vesting is complete. When that occurs, the shares are still subject to forfeiture and a separate tax election — an 83(b) election — may be available to elect taxation at the time of exercise rather than waiting for vesting to remove the forfeiture restriction. Early exercise and the 83(b) election are related but distinct decisions that require separate evaluation based on the specific grant terms.
Illustrative: An employee exercises 10,000 ISOs with an exercise price of $5.00 when the fair market value is $35.00.
• Bargain element: $30.00 per share × 10,000 shares = $300,000 AMT preference item.
• No ordinary income is recognized for regular tax purposes at exercise.
• The $300,000 is included in AMT income. Depending on total income and AMT exemption, this may produce a significant AMT liability.
• The AMT paid may generate a credit usable in future years when regular tax exceeds AMT.
Key assumption: AMT exemption and phase-out depend on total income and filing status. Projection before exercise, not after, is essential. Actual results vary.
Non-Qualified Stock Options (NSOs)
NSOs are the more common option type in startups and private companies, and simpler than ISOs from a tax standpoint. When an NSO is exercised, the spread between the exercise price and the fair market value at exercise is recognized as ordinary income, reported on your W-2, and subject to income tax and payroll taxes in the year of exercise. There is no AMT issue with NSOs.
After exercise, shares have a cost basis equal to the exercise price plus the ordinary income recognized. Subsequent sale produces capital gain or loss based on that adjusted basis, with the long-term versus short-term distinction depending on the holding period after exercise.
NSOs can be granted to employees, consultants, and directors. The income recognized at exercise is ordinary income regardless of how long the option was held before exercise. The planning question is primarily about timing: when to exercise, how much in a given year, and how the ordinary income recognized at exercise interacts with other income sources and withholding.
Illustrative: An employee exercises 5,000 NSOs with an exercise price of $10.00 when the fair market value is $40.00.
• Spread recognized as ordinary income: $30.00 × 5,000 = $150,000.
• This $150,000 appears on the W-2 and is subject to income tax and payroll taxes in the year of exercise.
• Cost basis in the shares after exercise: $40.00 per share (exercise price + income recognized).
• If held more than one year after exercise and then sold at $55.00, the $15.00 gain per share is long-term capital gain.
Key assumption: state income taxes apply separately and vary by state. Actual results depend on total income, filing status, and payroll tax treatment.
Employee Stock Purchase Plans (ESPPs)
ESPPs allow employees to purchase company stock at a discount, typically 15% below the lower of the stock price at the beginning or end of the offering period. The tax treatment depends on whether the sale qualifies as a qualifying or disqualifying disposition.
In a qualifying disposition — shares held for at least two years from the offering date and at least one year from the purchase date — the discount portion is taxed as ordinary income in the year of sale, and any remaining gain is long-term capital gain. In a disqualifying disposition, the spread between the purchase price and the fair market value at purchase is recognized as ordinary income in the year of sale, and any remaining gain is taxed at short- or long-term capital gain rates depending on the holding period after purchase.
ESPPs are often treated as straightforward employee benefits rather than tax planning decisions. Employees who sell ESPP shares without tracking their holding periods from both the offering date and the purchase date sometimes misreport or overlook the ordinary income component.
Illustrative: An employee purchases ESPP shares at $34.00 (15% discount from a $40.00 price at offering start) and sells within one year of purchase at $45.00.
• Because the sale occurs before the one-year holding period from purchase date, this is a disqualifying disposition.
• Ordinary income recognized: fair market value at purchase ($40.00) minus purchase price ($34.00) = $6.00 per share.
• Remaining gain: $45.00 sale price minus $40.00 FMV at purchase = $5.00 per share, taxed as short-term capital gain (held less than one year).
• The $6.00 ordinary income per share may or may not appear on the W-2 depending on plan administration.
Key assumption: offering and purchase dates, holding periods, and FMV at each date must be tracked accurately. Actual tax results depend on full-year income and filing status.
Further reading:
→ IRS overview of stock option taxation: IRS Topic No. 427 — Stock Options
→ IRS guidance on taxable and nontaxable income (covers RSUs and ESPPs): IRS Publication 525
→ IRS guidance on employee stock purchase plans: IRS Topic No. 423 — Employee Stock Purchase Plans
The most consequential decisions around equity compensation happen before the vest or exercise, not after. By the time the transaction closes, most of the planning options have already closed with it.
Withholding gaps and estimated taxes
Equity compensation income — whether from RSU vesting, NSO exercise, or ESPP sales — often creates withholding shortfalls. Employers withhold at standard supplemental rates that may be well below the actual marginal rate for an employee with significant base salary, prior equity events, or other income in the same year. The gap between what was withheld and what is owed accumulates during the year and becomes visible at filing time.
For employees with meaningful equity compensation income, quarterly estimated tax payments may be required to avoid underpayment penalties. The calculation is not simply how much was received but what total income for the year will be and what has already been withheld across all sources. That requires knowing where total income will land before the year ends.
AMT exposure from ISO exercises
The alternative minimum tax is most commonly triggered by ISO exercises, because the bargain element is an AMT preference item. For employees considering a large ISO exercise, projecting the AMT liability before exercising is essential. The AMT calculation involves a separate rate structure, different exemptions, and different income inclusions than regular income tax.
AMT paid in one year generates a credit usable in future years when regular tax exceeds AMT. The credit does not disappear, but it may take years to use depending on the employee’s income and tax situation. The near-term cost should be modeled before exercise, not discovered at filing time.
→ IRS guidance on the alternative minimum tax: IRS Topic No. 556 — Alternative Minimum Tax
→ IRS Form 6251 — Alternative Minimum Tax for Individuals: IRS Form 6251 and Instructions
Holding periods and the capital gain transition
For RSUs, ISOs, NSOs, and ESPPs alike, the holding period after the taxable event determines whether subsequent gain is short-term or long-term. Long-term treatment requires holding for more than one year. The difference in tax rates between short-term gain, taxed as ordinary income, and long-term gain, taxed at preferential rates, can be substantial for employees in higher brackets.
The decision about when to sell is a combination of tax planning and concentration risk management. Holding for long-term treatment is not always the right answer if it means maintaining a large concentrated position in employer stock. The tax benefit of preferential rates needs to be weighed against the risk of the position declining in value while the holding period runs.
NIIT and income stacking
The net investment income tax applies a 3.8% surtax on investment income for taxpayers above certain modified adjusted gross income thresholds. Capital gains from equity compensation sales are investment income subject to this tax. In a year with significant equity events, total income may cross the NIIT threshold even if it would not in a typical year.
Equity compensation income also interacts with other income-based thresholds: deduction phaseouts, Roth IRA contribution limits, Medicare surtaxes, and state-specific rules. A vesting or exercise event that looks straightforward in isolation can affect the tax treatment of other items across the return in ways that are not visible without seeing the full picture.
For employees who lived or worked in more than one state during the grant, vesting, or exercise period, state tax treatment may not follow current residence alone. Many states assert the right to tax equity compensation income sourced to periods of employment or service performed within the state, regardless of where the employee lives when the vest or exercise occurs. California, New York, and several other states apply sourcing rules that can produce state tax obligations in states where the employee no longer lives.
For employees who have relocated, changed employers, or worked remotely across state lines while equity was accruing, reviewing state sourcing and withholding before filing can be as important as the federal analysis. The interaction between state sourcing rules and the ordinary income recognition at vesting or exercise is one of the less visible but practically significant equity compensation issues for higher-income professionals.
For some startup employees or founders who acquire stock at original issuance from a qualifying C corporation, the Section 1202 qualified small business stock (QSBS) rules may affect the tax treatment of a later sale. If the stock qualifies and the holding period and other requirements are met, a meaningful exclusion from federal capital gains tax may be available on a sale.
QSBS is a separate analysis from the ordinary income and AMT questions covered in this article. It involves its own eligibility rules around original issuance, C-corporation status, active business requirements, and holding period. But it is important enough to identify before an exercise or sale decision is made, because the conditions for qualification need to be in place before the triggering event, not identified after. A future article will cover the QSBS analysis in more detail.
Concentration and timing decisions
Many employees accumulate significant positions in employer stock through RSUs, options, and ESPPs over time without actively deciding to do so. Each vesting event adds shares; each grant adds more. The result is a concentrated position with a complex basis history across multiple lots with different holding periods and cost basis levels.
Decisions about when to sell, how much to sell, and in what order to dispose of shares from different lots are planning decisions that affect both the tax outcome and the investment risk profile. These decisions are easier to make with full information about basis, holding periods, and the current-year tax picture than they are to reconstruct after the fact.
Do RSUs count as ordinary income?
Yes. The fair market value of RSU shares on the vesting date is recognized as ordinary income, reported on your W-2, and subject to income tax and payroll taxes in the year of vesting. This income is taxed the same way as wages. After vesting, if you hold the shares and they appreciate further, the subsequent gain is a capital gain. If you sell immediately at vesting, the capital gain component is zero or minimal.
Should I exercise ISOs early?
Exercising ISOs while the stock price is close to the exercise price minimizes the bargain element and therefore the AMT adjustment at exercise. It also starts the qualifying disposition holding period clock earlier, potentially qualifying the eventual sale for long-term capital gain treatment sooner. Some plans permit exercise before vesting is complete; when that occurs, an 83(b) election may be available to elect current taxation on the unvested shares rather than waiting for vesting to occur.
Whether early exercise makes sense depends on the spread at the time of exercise, the AMT implications, the likelihood that vesting conditions will be met, and the employee’s liquidity. It is not universally beneficial and requires analysis of the specific grant terms alongside the employee’s total tax picture.
What triggers AMT, and how do I know if I’m exposed?
The primary ISO-related AMT trigger is the bargain element at exercise — the difference between the exercise price and the fair market value on the exercise date. That amount is added to income for AMT purposes even though it is not recognized for regular tax. If total AMT income after exemptions exceeds the amount that would be taxed under the regular system, AMT applies.
The AMT exemption phases out at higher income levels, meaning high-income employees may have less exemption available to absorb the ISO bargain element. The only way to know whether a specific exercise will trigger AMT is to run the full projection with all income sources included, before exercising rather than after.
Why wasn’t my withholding enough when RSUs vested?
Employers typically withhold on supplemental income at a flat federal rate. If total income for the year puts you in a higher bracket, the flat withholding rate leaves a gap. In a year with multiple vesting events, that gap compounds across each one. The solution is requesting additional withholding from your employer, making quarterly estimated tax payments during the year, or both. The problem is usually predictable before the year ends, but only if total income is being tracked in real time rather than discovered at filing.
When does capital gain treatment begin for shares I received through equity compensation?
The capital gain holding period clock starts on the date the shares were delivered to you in a form that created a taxable event — the vesting date for RSUs, the exercise date for NSOs and ISOs. For ISOs, the qualifying disposition rules require both a one-year hold from the exercise date and a two-year hold from the grant date, so both dates matter. Selling before meeting both holding periods triggers ordinary income treatment on the gain that would otherwise qualify for long-term capital gain rates.
When shares from RSUs or ESPPs are sold, the broker typically reports the full sale proceeds on Form 1099-B with a cost basis that may not reflect the ordinary income already recognized at vest or purchase. If that ordinary income was reported on your W-2 and the broker’s basis is not adjusted to include it, the return can appear to show a gain larger than what you actually experienced. Failing to adjust the basis on the Schedule D entry results in paying tax twice on the same economic income — once as ordinary income at vesting and again as a capital gain at sale. The adjustment is required but not automatic, and it is one of the most common errors in equity compensation tax reporting.
Equity compensation creates planning opportunities at every stage — at grant, before vesting or exercise, and when deciding whether to hold or sell. But those opportunities are time-sensitive. Many of the decisions that affect the tax outcome close at the moment of vesting or exercise, not during tax filing season when the year’s transactions are already history.
For employees with multiple grants, multiple vesting dates, or both ISOs and RSUs in the same year, the interaction between instruments, holding periods, and the rest of the year’s income creates a picture that benefits from being looked at whole rather than piece by piece.
Want a clearer picture of how your equity compensation fits into your full tax situation?
Download Where Tax Returns Go Wrong — a guide to common gaps in more complex returns, including equity compensation, multi-source income, and planning coordination.
This article is general educational content. It is not tax advice and does not address any individual’s specific tax situation. Tax rules, rates, and thresholds change; verify current figures with IRS guidance or a qualified tax professional before making any decisions. Reading this article does not create a practitioner-client relationship with Clear Tax Compass.
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