Private Stock Options: How ISO, NSO, and RSU Equity Actually Works at Pre-IPO Companies

Private stock options are equity compensation instruments granted by privately-held companies that give employees, consultants, and board members the right to acquire ownership in the company at a predetermined strike price on a defined vesting schedule. The three dominant instruments are Incentive Stock Options (ISOs), Non-Qualified Stock Options (NSOs), and Restricted Stock Units (RSUs), each governed by separate sections of the Internal Revenue Code with materially different tax outcomes at grant, exercise, vest, and sale. Anyone holding private stock options at a venture-backed startup or pre-IPO company needs to understand at minimum: how the 409A valuation sets the strike price, when Alternative Minimum Tax (AMT) is triggered on an ISO exercise, what an 83(b) election does for early-exercised options, and how the long-term capital gains (LTCG) clock interacts with a future liquidity event.

This guide walks through ISO mechanics under IRC Section 422, NSO ordinary-income treatment under IRC Section 83, RSU double-trigger vesting under IRC Section 409A, 409A valuation methodology and the Discount for Lack of Marketability (DLOM), AMT calculation on Form 6251, the 30-day 83(b) election window, qualified small business stock under IRC Section 1202, and the decision framework employees use when planning an exercise around an IPO, tender offer, or acquisition. Every number, deadline, and statutory citation in this guide links back to the primary source: the U.S. Code, Treasury Regulations, IRS publications, or filings from the issuer of the equity comp data. If you are weighing whether to exercise at all, also read our companion piece on private company tender offers and our deep dive on QSBS Section 1202 small business stock.

What Private Stock Options Actually Are: The Three Instruments

At a privately-held company, “stock options” is shorthand for three distinct equity compensation instruments that the IRS treats very differently. ISOs are statutory options created by IRC Section 422 in 1981 and reserved for W-2 employees of the granting corporation or its parent or subsidiary. NSOs are everything else: any compensatory option that fails the ISO rules, governed by the general property-transfer rules of IRC Section 83. RSUs are not options at all but contractual promises to deliver shares (or cash equivalent) on a future vesting date, governed by both Section 83 and the nonqualified deferred compensation rules of IRC Section 409A. Companies often grant a combination across employee tenure: ISOs at hire when the 409A FMV is low, NSOs for excess above the $100,000 annual cap or for non-employee grants, and RSUs in the years immediately before an expected IPO when double-trigger structure becomes necessary.

The differences matter because they determine when tax is owed (grant, exercise, vest, or sale), what type of tax applies (ordinary income, AMT preference, or capital gains), and what happens at common life events (leaving the company, an IPO, an acquisition, or a tender offer). The next section is the side-by-side reference table; the eleven sections after that drill into each mechanic with statutory citations and worked examples.

Quick Comparison: ISO vs NSO vs RSU at a Glance

The fastest way to internalize the three instruments is to look at them side by side on the seven decision points that actually drive employee outcomes: who can receive them, when tax is owed, whether AMT applies, and what happens if you leave the company. The table below summarizes the statutory rules. Each row links to the deep-dive section further down in this guide.

Attribute	ISO (Incentive Stock Option)	NSO (Non-Qualified Stock Option)	RSU (Restricted Stock Unit)
Statutory authority	IRC Section 422	IRC Section 83	IRC Sections 83 and 409A
Who can receive	W-2 employees only	Employees, consultants, board members	Employees (typically W-2)
Tax at grant	None	None (if priced at FMV)	None
Tax at exercise / vest	None for regular tax; AMT preference on bargain element	Ordinary income on bargain element (FMV minus strike)	Ordinary income on FMV at vest (no exercise required)
Tax at sale	LTCG if 2-year-grant plus 1-year-exercise hold met	Capital gain or loss from FMV at exercise to sale price	Capital gain or loss from FMV at vest to sale price
AMT exposure	Yes, on bargain element at exercise	No	No
83(b) election available	Only if early-exercised before vesting	Only if early-exercised before vesting	No (no purchase to elect on)
Early exercise possible	Yes, if plan permits	Yes, if plan permits	No
Standard expiration post-departure	90 days (statutory for ISO treatment)	Plan-dependent, often 90 days to 10 years	Forfeit unvested at departure
Max term	10 years from grant	Typically 7 to 10 years	Plan-dependent
$100K annual vest cap	Yes; excess converts to NSO	None	None

Read the table this way: ISOs are the most tax-favored on paper but carry AMT risk and rigid holding rules. NSOs are simpler and more flexible but trigger ordinary income at exercise. RSUs require no out-of-pocket exercise cost but generate a tax bill the moment shares vest, which at a private company can mean owing tax on illiquid stock unless the grant uses double-trigger vesting. The IRS confirms the basic framework in Publication 525, Taxable and Nontaxable Income, which is the most accessible primary reference for the day-to-day W-2 employee.

ISO Deep Dive: Section 422 Requirements, $100K Cap, and Holding Periods

Incentive Stock Options are creatures of IRC Section 422. The statute imposes seven hard requirements on the issuer and the grantee for the option to qualify for ISO treatment. Miss any one and the option is treated as an NSO for tax purposes, which usually means ordinary income at exercise instead of the favorable capital-gains-on-sale outcome employees expect.

Requirement 1: Employee status. Section 422(a)(2) requires the grantee to be an employee of the issuing corporation or a parent or subsidiary, from grant through the date three months before exercise. Consultants, advisors, and non-employee directors cannot receive ISOs. If a company grants what it calls an ISO to a 1099 contractor, the grant is automatically an NSO regardless of how the paperwork reads.

Requirement 2: Plan documentation. The ISO must be granted under a written plan approved by shareholders within 12 months before or after the board adopts the plan, per Section 422(b)(1). The plan must specify the aggregate share pool and the class of employees eligible.

Requirement 3: Strike price at FMV. Section 422(b)(4) requires the strike price to be at least fair market value (FMV) on the grant date. For a private company, FMV is established by a 409A valuation. For 10%-or-greater shareholders, the strike must be at least 110% of FMV and the term cannot exceed 5 years, per Section 422(c)(5).

Requirement 4: 10-year maximum term. Section 422(b)(3) caps the term at 10 years from grant. Companies often issue ISOs with a 10-year term to maximize optionality.

Requirement 5: $100,000 annual vest cap. Section 422(d) caps the aggregate FMV (measured at grant) of ISOs that first become exercisable in any calendar year at $100,000 per employee. Anything above the cap is automatically NSO. A grant of 40,000 options at a $5 strike with all shares vesting on a 1-year cliff would have $200,000 first becoming exercisable in year 1, meaning $100,000 worth converts to NSO. Standard 4-year monthly vesting with a 1-year cliff usually stays under the cap unless the strike is unusually high or the grant is unusually large.

Requirement 6: Holding period for LTCG. Section 422(a)(1) requires the shares to be held at least 2 years from grant and 1 year from exercise to qualify as a “qualifying disposition” eligible for long-term capital gains treatment on the spread above the strike price. Selling before either holding period is satisfied is a “disqualifying disposition,” which converts the bargain element at exercise into ordinary income, taxed at W-2 rates.

Requirement 7: 90-day post-termination exercise window. Section 422(a)(2) and Treasury Regulation 1.421-1(h) require exercise within 3 months (90 days for most plans) of employment termination for ISO treatment to apply. Some companies have extended this window in the equity plan (sometimes to 7 or 10 years) but doing so converts the option to an NSO after the 90th day. Cooley, Wilson Sonsini, and Fenwick have all published detailed memos on the trade-off.

The big swing factor on ISOs is the AMT preference item at exercise. Even though no regular-tax income is recognized, the bargain element (FMV at exercise minus strike) is added to Alternative Minimum Taxable Income on Form 6251. We cover the AMT math in a dedicated section below.

NSO Deep Dive: Ordinary Income at Exercise and W-2 Withholding

Non-Qualified Stock Options are the default category. Anything that fails Section 422 is an NSO, and NSOs operate under the general IRC Section 83 framework that governs property transferred in connection with services. Treasury Regulation 1.83-7 specifically addresses options without a readily ascertainable fair market value, which describes essentially all private company NSOs.

Who can hold them. NSOs can be granted to anyone: employees, 1099 consultants, advisors, board members, and even vendors in some cases. There is no shareholder-approval requirement at the federal tax level (state corporate law and the company’s equity plan still apply).

Tax at grant. No tax at grant, provided the strike is at FMV. If the strike is below FMV on the grant date, the option violates IRC Section 409A and the employee faces immediate income recognition plus a 20% federal penalty plus interest, per Section 409A(a)(1)(B). This is why a defensible 409A valuation is non-negotiable for private companies.

Tax at exercise. The bargain element (FMV at exercise minus strike price) is ordinary W-2 wages for an employee or self-employment income for a contractor. For an employee NSO exercise, the company is required to withhold federal income tax, FICA (Social Security and Medicare), and applicable state tax at the supplemental wage rate (22% federal in 2026 for amounts up to $1 million, 37% above per IRS guidance in Publication 15). The bargain element appears in Box 1 of the W-2 with a Code V entry in Box 12 to flag it.

Tax at sale. Once shares are held, the cost basis is the FMV at exercise (not the strike price). Gain from FMV-at-exercise to sale price is capital gain, long-term if held more than 12 months. Loss is capital loss. This is the same basic mechanic as buying any other stock, just with a non-cash element in the basis calculation.

Post-termination window. Because NSOs have no statutory 90-day rule, companies are free to grant 7-year or 10-year post-termination exercise windows. Pinterest, Quora, and Coinbase have all publicly extended exercise windows for departing employees, as documented by NPR coverage of Pinterest’s 2015 policy change. The trade-off: extending an ISO past 90 days converts it to an NSO, so an extension is a feature of NSOs more than a tax-neutral change to ISOs.

NSOs are the dominant instrument at later-stage private companies and at companies that grant equity to non-employees. A consultant board member at a Series C startup will almost always receive NSOs even if the same company grants ISOs to W-2 engineers. The flexibility comes at the cost of upfront ordinary income at exercise, which can be a six-figure tax bill on illiquid shares.

RSU Deep Dive: Promise of Future Shares and Double-Trigger Vesting

Restricted Stock Units are not options. An RSU is a contractual promise by the company to deliver one share (or cash equivalent) at a future date when vesting conditions are met. There is no strike price, no exercise, and no out-of-pocket cost to the employee. RSUs are governed by IRC Section 83 for the property-transfer rules and IRC Section 409A for the timing rules on deferred compensation.

Tax at vest. Ordinary income equal to the FMV of the shares on the vest date. This is W-2 wages, subject to federal income tax, FICA, and state tax withholding. Public companies typically satisfy withholding through “sell-to-cover”: the broker automatically sells a portion of vested shares to cover the tax bill. Private companies cannot sell-to-cover because there is no public market, which is precisely why pre-IPO companies switched to double-trigger vesting.

Double-trigger vs single-trigger. Double-trigger RSUs vest only when two conditions are met: a time-based condition (typically 4 years with a 1-year cliff) AND a liquidity event (IPO, acquisition, or tender offer). This structure was popularized by Facebook in the late 2000s and is now standard at Stripe, Databricks, SpaceX, and most mature pre-IPO companies, as documented in Carta’s research on RSU structures. Single-trigger RSUs vest on time alone, which means employees recognize ordinary income on illiquid shares with no way to sell to cover the tax bill. Single-trigger is now rare at private companies for exactly this reason.

Capital gains from vest forward. Once shares vest, the cost basis is the FMV at vest. Any gain from vest-price to sale-price is capital gain, long-term if held more than 12 months after vest. The vesting date starts the LTCG holding clock.

Section 83(i) deferral. The 2017 Tax Cuts and Jobs Act added IRC Section 83(i), which allows certain employees of eligible private companies to defer the ordinary income on RSU vest for up to 5 years. The election has narrow eligibility (the company must offer it to at least 80% of US employees, and excluded employees include 1% owners, the CEO, CFO, and the four highest-paid officers) and substantial administrative complexity. AICPA and Bloomberg Tax have both observed that uptake has been minimal because companies do not want to track 5 years of deferred income across employee turnover.

No 83(b) election available. Because there is no transfer of property at grant (only a contractual promise of future shares), there is nothing to elect on. Employees sometimes ask about 83(b) for RSUs and the answer is simply “not available.” If the employer offers restricted stock (actual shares subject to forfeiture) instead of RSUs, that is a different instrument and 83(b) does apply. Treasury Regulation 1.83-2 governs the election in detail.

RSUs are the dominant late-stage and public-company instrument. Pre-IPO, double-trigger RSUs are common from Series D onward and almost universal in the year before an expected IPO. Earlier-stage employees usually hold ISOs or NSOs because the company has not yet structured an RSU program.

The 409A Valuation: Strike Price, DLOM, and Audit Risk

Every private company that grants equity-based compensation needs a defensible fair market value for its common stock. IRC Section 409A, enacted as part of the American Jobs Creation Act of 2004, treats below-FMV stock options as nonqualified deferred compensation, triggering immediate income inclusion plus a 20% federal penalty plus interest on the employee. Treasury Regulation 1.409A-1(b)(5)(iv)(A) provides the safe harbor: an “independent appraisal” by a qualified appraiser within the preceding 12 months creates a presumption of reasonable FMV that the IRS can rebut only by showing the valuation was “grossly unreasonable.”

The 12-month rule and material events. A 409A appraisal is valid for 12 months OR until a “material event” occurs, whichever is sooner. Material events include a priced equity round, a major acquisition or divestiture, a significant change in financial performance, the hiring or departure of key executives, an IPO filing, and any event the board believes would meaningfully change FMV. After a Series B round, for example, the company needs a fresh 409A even if the prior one is only 4 months old.

Common stock vs preferred stock pricing. Investors buy preferred stock that carries liquidation preference, anti-dilution rights, voting rights, and other economic and governance rights. Employees receive common stock. The common stock FMV is materially below the preferred stock price per share, often 20% to 40% lower. The gap arises from the rights gap and from the Discount for Lack of Marketability.

Discount for Lack of Marketability (DLOM). DLOM accounts for the illiquidity of private company shares. Appraisers calculate DLOM using option-pricing models (Finnerty, Chaffe, Longstaff), Pre-IPO studies, and Restricted Stock Studies. The 2024 AICPA practice aid “Valuation of Privately-Held-Company Equity Securities Issued as Compensation” (commonly called the AICPA Cheap Stock guide) is the canonical reference and recommends DLOM in the 15% to 35% range for typical venture-backed private companies, with extreme cases reaching 40% to 50% for very early or distressed companies.

Stage	Typical Preferred-to-Common Discount	Typical DLOM	Common Stock FMV as % of Preferred
Seed / Series A	50% to 80%	30% to 40%	10% to 25%
Series B / Series C	40% to 60%	25% to 35%	20% to 40%
Series D / pre-IPO	25% to 40%	15% to 25%	40% to 60%
IPO filed (S-1)	5% to 15%	5% to 15%	70% to 90%

Source: AICPA Accounting and Valuation Guide, Valuation of Privately-Held-Company Equity Securities Issued as Compensation (2024 edition), aggregated industry practice.

Vendor landscape. The 409A appraisal market is dominated by Carta (the largest cap-table software company), Pulley, Diligent Equity, Aprio, Andersen Tax, and Houlihan Lokey on the higher end. Pricing ranges from approximately $2,000 to $5,000 for software-driven valuations (Carta, Pulley) and $8,000 to $25,000 for white-glove independent appraisals (Houlihan Lokey, Duff and Phelps now Kroll). Carta’s own pricing page and Pulley’s pricing breakdown confirm these bands.

Audit risk. An IRS challenge that the 409A was “grossly unreasonable” places the burden of proof on the company to demonstrate the methodology. Penalties for under-strike options are draconian: 20% federal additional tax plus interest plus immediate ordinary income recognition on the deferred comp, all on the employee, per Section 409A(a)(1). For this reason, companies almost always engage a qualified independent appraiser rather than rely on internal estimates.

Alternative Minimum Tax on ISO Exercise: The Form 6251 Calculation

The single biggest reason employees underestimate the cost of exercising ISOs is Alternative Minimum Tax. Regular income tax owes nothing at ISO exercise. But the bargain element (FMV at exercise minus strike) is an AMT preference item under IRC Section 56(b)(3), which means it gets added to Alternative Minimum Taxable Income on Form 6251 and taxed at AMT rates of 26% on AMTI up to $232,600 (2026 single-filer threshold per IRS Revenue Procedure 2025-32) and 28% above.

Worked example. Employee holds 10,000 ISOs with a $1.00 strike price, granted 3 years ago when the 409A FMV was $1.00. The current 409A FMV is $10.00. Employee exercises all 10,000 ISOs by paying $10,000 in cash to the company. The bargain element is ($10.00 minus $1.00) times 10,000 shares = $90,000.

Tax Calculation	Regular Tax Path	AMT Path
Employee W-2 wages	$200,000	$200,000
ISO bargain element added?	No	Yes, $90,000
Adjusted gross income	$200,000	$290,000 (AMTI before exemption)
Standard / AMT exemption (2026 single)	$15,750	$90,300 (subject to phase-out above $642,100)
Taxable income	$184,250	$199,700
Rate	22% to 32% bracket	26%
Tax owed (approximate)	$38,000	$51,922
Net AMT owed = AMT minus regular	n/a	$13,922

Source: 2026 federal tax rates and AMT exemption from IRS Revenue Procedure 2025-32. Example assumes single filer, no other AMT preferences.

AMT credit recovery. AMT paid on ISO exercise creates a Minimum Tax Credit under IRC Section 53 that the taxpayer can claim in future years when regular tax exceeds tentative AMT. The credit is non-refundable but carries forward indefinitely. In practice, employees who sell ISO shares in a qualifying disposition often recover the AMT credit over the following 3 to 7 years as regular-tax capital gains create AMT “headroom.”

Same-year disqualifying disposition. If the employee exercises and sells in the same calendar year, the transaction is a disqualifying disposition (fails the 1-year-from-exercise rule by definition). The bargain element becomes ordinary W-2 income but does NOT create an AMT preference. For an employee in a 35% regular bracket who would have owed AMT anyway, same-year exercise-and-sell is often the simpler path. For an employee with high conviction the stock will appreciate, paying AMT and starting the LTCG clock is the higher-EV bet but carries the risk of paying AMT on a stock that later collapses.

The “AMT lottery ticket” framework. Pre-IPO employees often exercise ISOs early when the 409A FMV is close to the strike price, minimizing the bargain element and therefore the AMT bill. A 10,000-share ISO exercise at a $1 strike and a $1.10 FMV creates only $1,000 of AMT preference. The same 10,000 shares exercised 2 years later at a $10 FMV creates $90,000 of preference. The trade-off is the cash outlay of $10,000 today and the risk of total loss if the company fails. Michael Kitces and Carta’s exercise strategies guide both walk through the math in more detail.

Early Exercise and the 83(b) Election: 30-Day Deadline

Early exercise lets an employee buy unvested option shares now and put them in escrow, subject to the company’s right to repurchase the unvested portion at the original strike price if the employee leaves. Combined with a timely 83(b) election, early exercise can collapse the option into restricted stock with the LTCG clock starting today.

The 83(b) mechanic. Section 83(b) of the Internal Revenue Code allows a service provider receiving restricted property to elect to recognize ordinary income on the property at the time of transfer, rather than at the time the restrictions lapse. For early-exercised options where the strike price equals current FMV, the ordinary income amount is zero (FMV minus purchase price equals zero). The election locks in the cost basis at the strike price and starts the long-term capital gains holding period immediately.

30-day filing deadline. Treasury Regulation 1.83-2(c) requires the 83(b) election to be filed with the IRS within 30 days of the property transfer. The deadline is absolute. The IRS has no discretion to grant extensions. A late 83(b) is invalid, full stop. The election must be sent to the IRS service center where the taxpayer files, with a copy retained for personal records and a copy provided to the employer.

What goes in the election. The IRS published a sample 83(b) election form in Revenue Procedure 2012-29 that includes the required items: taxpayer name and SSN, description of property, date of transfer, taxable year, restrictions, FMV at transfer, amount paid, and amount being included in income.

Filing logistics. Historically the election had to be filed by certified mail with return receipt requested. The IRS began accepting electronic submission of 83(b) elections through certain e-filing platforms in 2024, per IRS announcements in mid-2024, but the safest practice remains certified mail with a green return receipt as proof of timely filing.

Risk and reward. If the company appreciates 10x, the early-exercise plus 83(b) holder pays LTCG (20% federal plus 3.8% NIIT, 23.8% combined for high earners) on the entire spread, versus an ordinary-income path that costs 37% federal plus state. On 10,000 shares moving from $1 to $10, the tax delta is ($90,000 times (0.37 minus 0.238)) = $11,880 saved by going LTCG. If the company fails, the early-exerciser loses the $10,000 cash outlay and recognizes a capital loss limited to $3,000 per year against ordinary income.

Cooley’s 83(b) FAQ, Wilson Sonsini’s founder equity primer, and Gunderson Dettmer’s early exercise memo are the standard practitioner references on the mechanics.

Vesting Schedules: 4-Year Cliff, Acceleration, and IPO Triggers

The Silicon Valley default since the late 1990s has been a 4-year vesting schedule with a 1-year cliff and monthly vesting thereafter. Andreessen Horowitz, Sequoia, and Y Combinator all default to this structure in their standard term-sheet templates, and Carta’s annual State of Equity report documents that more than 90% of venture-backed startups still use 4-year vesting as of 2025.

Standard 4-year monthly with 1-year cliff. Employee gets nothing at month 11. At month 12, 25% of the grant vests in one chunk. From month 13 through month 48, the remaining 75% vests in 36 equal monthly tranches of approximately 2.083% each.

Vesting Variant	Cliff	Total Term	Common Use
4-year monthly, 1-year cliff	1 year	4 years	Default for new hires (employee + advisor)
4-year monthly, no cliff	None	4 years	Founders, occasionally senior execs
4-year quarterly, 1-year cliff	1 year	4 years	Some later-stage companies (admin simplicity)
5-year monthly, 1-year cliff	1 year	5 years	Snap (pre-IPO), some longer-horizon startups
3-year accelerated (33/33/33)	None or 6 months	3 years	Senior hires negotiating shorter horizon
Milestone-based	Performance gate	Variable	Founders earning back equity, performance grants

Acceleration provisions. Two main flavors. Single-trigger acceleration vests a defined percentage (often 25% to 100%) upon a Change in Control (CIC). Double-trigger acceleration vests upon a CIC AND a subsequent qualifying termination (typically termination without cause or resignation for good reason within 12 to 24 months of close). Double-trigger is far more common because it protects the employee against post-acquisition layoffs without giving the acquirer’s retention rationale a free haircut.

IPO acceleration. Most plans do NOT accelerate vesting at IPO. The IPO is treated as an ordinary liquidity event, the lockup applies, and unvested shares continue to vest on schedule. Some senior executives negotiate explicit IPO acceleration as part of their offer, but this is the exception rather than the rule. Cooley’s equity acceleration overview covers the negotiation dynamics in depth.

Tax on Exit: IPO, Acquisition, and Tender Offers

The whole point of private stock options is the exit. Three pathways dominate: an Initial Public Offering followed by a lockup, a strategic or private-equity acquisition (cash, stock, or mixed consideration), and a pre-IPO secondary tender offer.

IPO and the 180-day lockup. The standard IPO lockup, mandated by the underwriting agreement rather than by SEC rule, prohibits insiders and pre-IPO shareholders from selling for 180 days after the offering date. Some companies (Airbnb’s December 2020 IPO is the canonical example) have used staggered lockups, releasing employee shares as early as the second-quarter earnings call if the stock holds above a target price. After lockup expiry, employees can sell vested shares freely subject to insider-trading rules and 10b5-1 plan disclosures. The SEC’s 10b5-1 guidance and the December 2022 amendments to Rule 10b5-1 (90-day cooling-off period for officers and directors) govern the trading-plan mechanics.

Acquisition for cash. Vested options usually get cashed out at the deal price minus the strike. Unvested options either accelerate per the plan or roll over into an acquirer instrument. Cash consideration is taxable in the year of close: bargain element on NSOs is ordinary income, ISO disposition rules apply to ISOs, and RSU shares already taxed at vest are now taxed on the cash spread above vest-FMV as capital gain.

Acquisition for stock. An all-stock deal that qualifies as a tax-free reorganization under IRC Section 368 lets shareholders defer recognition of gain. The acquirer’s stock takes a carryover basis from the target stock. This is how Salesforce-Slack, Microsoft-LinkedIn, and many strategic acquisitions structure consideration to defer the tax bill.

280G golden parachute risk. IRC Section 280G imposes a 20% excise tax on “excess parachute payments” to executives and other “disqualified individuals” if the aggregate change-in-control payments exceed 3x the individual’s 5-year base amount. Acceleration of vesting counts toward the threshold. Companies often run a 280G analysis before signing a deal and may require a shareholder vote (private-company exception under Section 280G(b)(5)) to cleanse the payments.

Tender offers and secondary sales. Pre-IPO tender offers let employees sell a defined percentage (commonly 10% to 25%) of vested shares to incoming investors or to the company at a negotiated price, typically the most recent preferred round price minus a discount. Stripe ran the largest pre-IPO tender in tech history in 2023 and again in 2025; SpaceX runs semi-annual tenders. Read our full breakdown in our Stripe tender offer guide and our primer on private company tender offers.

QSBS Section 1202: The $10 Million Federal Exclusion

If the exit produces a large capital gain on stock acquired directly from a domestic C corporation, IRC Section 1202 can exclude up to $10 million OR 10 times the taxpayer’s adjusted basis in the stock, whichever is greater, from federal capital gains tax. The exclusion is one of the most powerful tax provisions in the Code for private-company employees who exercise early.

Five-year holding requirement. Section 1202(a)(1) requires the taxpayer to hold the qualified small business stock (QSBS) for more than 5 years before sale. The clock starts on the date the stock is issued (the exercise date for options, the grant date for actual restricted stock subject to an 83(b) election). This is why early exercise plus 83(b) is the canonical QSBS strategy: it starts the 5-year QSBS clock immediately at a near-zero basis.

Issuer-side requirements. Section 1202(c) requires the issuer to be a domestic C corporation with gross assets of $50 million or less at the time of issuance (immediately before and after, per Section 1202(d)). The company must be engaged in an active business, defined in Section 1202(e) to exclude services in health, law, engineering, accounting, finance, consulting, brokerage, and certain other professional fields. SaaS, biotech R&D, fintech engineering, and most product-driven startups generally qualify; pure professional services partnerships generally do not.

The One Big Beautiful Bill Act changes. The 2025 legislation amended Section 1202 to raise the asset cap from $50 million to $75 million and the exclusion cap from $10 million to $15 million for stock acquired after the enactment date, with phased exclusion at 50% for 3-year holds, 75% for 4-year holds, and 100% for 5-year holds. The pre-existing 100% exclusion for stock issued after September 27, 2010 remains in place for that issuance window. Our QSBS guide covers the 2025 changes in depth.

State conformity. California explicitly does not conform to Section 1202 (Cal. Rev. & Tax. Code Section 18152.5 was repealed for tax years beginning on or after January 1, 2013 per California Franchise Tax Board guidance). New Jersey, Pennsylvania, Mississippi, and Alabama also do not conform. New York partially conforms. Most other states follow federal treatment automatically.

QSBS stacking. The $10 million (or $15 million post-2025) per-issuer cap is per-taxpayer, which means gifts to family members or to non-grantor trusts created for family members can each access their own cap. A founder with $50 million of QSBS gain can gift portions to a spouse and to non-grantor trusts for children, multiplying the exclusion by the number of separate taxpayers. This is the “QSBS stacking” strategy that wealth advisors at Morgan Stanley at Work, JPMorgan Workplace Solutions, and Zajac Group routinely recommend.

Exit Decision Framework: When to Exercise

The most expensive mistake employees make is exercising at the wrong time. There is no universal right answer, but the framework collapses to four scenarios.

Scenario	Typical Exercise Decision	Rationale
Just-vested grant, pre-Series B, low FMV	Exercise + 83(b) on entire vested + unvested if cash allows	Bargain element is near zero; start QSBS + LTCG clock at low cost
Pre-IPO with tender offer announced	Wait for tender; exercise only what will be sold + held	Use tender proceeds to fund exercise + AMT bill; avoid uncovered tax exposure
Pre-IPO without tender, 2+ years to expected IPO	Exercise enough to hit 1-year LTCG and 5-year QSBS by IPO	Plan backward from expected exit; layer in exercises across 2 to 4 years
Post-IPO before lockup expires	Cannot sell; can exercise NSOs but ordinary income hits now	Usually wait until lockup expires to coordinate exercise + sale
Post-IPO after lockup, diversifying	Exercise + sell-to-cover taxes; hold remainder for LTCG	Concentration risk usually exceeds tax savings; sell to diversify
Leaving company, ISOs in plan	Decide before 90-day window closes; model AMT carefully	Post-90-day ISO converts to NSO and likely expires

The “leave on the table” math. Holding concentrated private-company stock through an exit usually outperforms diversifying, but the variance is enormous. Carta’s 2024 employee equity outcomes study found that the median realized value per equity holder was less than 50% of the value on the original grant statement, and that more than 30% of vested options at venture-backed startups expired worthless. Concentration risk is real. Most wealth managers recommend capping single-company illiquid equity at 20% of net worth post-exit and diversifying the rest.

Modeling the AMT bill before exercise. Run a Form 6251 calculation with your specific filing status, state tax, other income, and proposed exercise size. Several free tools (Carta’s exercise calculator, AMT.tax, ESO Fund’s calculator) and most CPAs can run the scenario. The single largest source of unexpected tax bills is exercising in December without modeling AMT, then receiving a 5-figure bill in April with no liquid shares to sell.

Five Common Private Stock Option Mistakes

Mistake 1: Missing the 30-day 83(b) deadline. The Treasury Regulation 1.83-2(c) deadline is absolute. There is no grace period, no late-filing penalty option, no IRS discretion to grant relief. A late 83(b) is simply invalid, which means the ordinary-income-at-vest path applies and the LTCG clock starts at each vest date rather than at exercise. The “Tax Court has consistently refused equitable relief,” per a 2023 Bloomberg Tax analysis of Section 83(b) deadline jurisprudence. Hand-deliver to a USPS clerk on day 29 if needed.

Mistake 2: Accidentally disqualifying an ISO disposition. Selling ISO shares before the 2-year-from-grant and 1-year-from-exercise holding periods are both satisfied converts the gain to ordinary income. Many employees sell at the lockup expiry post-IPO without checking that 1 year has passed since exercise. A 90-day-pre-IPO exercise followed by a 180-day-lockup sale is a disqualifying disposition: 270 days, not 365.

Mistake 3: Letting the 90-day post-departure exercise window expire. Many former employees focus on their next role and forget that their unexercised ISOs expire 90 days after termination per Section 422(a)(2). If the company has not had a liquidity event and the 409A FMV is meaningfully above strike, the employee may need to find $50,000 to $500,000 in cash to exercise before the window closes. Companies like Coinbase and Pinterest have extended these windows, but most have not. Plan the cash years in advance.

Mistake 4: Not modeling AMT before a large exercise. A six-figure AMT bill in April on shares the employee cannot sell is the single most common “private equity disaster story” in financial-planning literature. Always run Form 6251 before exercising, ideally in October or November so there is time to either reduce the exercise size or arrange financing through an ESO Fund-style non-recourse exercise loan.

Mistake 5: Concentration risk above 20% of net worth. The behavioral pull to hold concentrated equity in a company the employee believes in is enormous, but the data is clear: even venture-backed pre-IPO companies that reach an IPO often lose 40% to 60% of peak value within 2 years post-lockup. Diversification after a liquidity event is usually the right move. The Boglehead-style rule of thumb that single-stock holdings should stay under 5% to 10% of net worth applies even more strongly to illiquid private stock that carries forced-hold restrictions.

TLDR: Seven Takeaways on Private Stock Options

The seven decision-stage bullets every private-company employee should internalize before signing the offer letter or planning a year-end exercise.

1. Know which instrument you hold. ISOs (Section 422), NSOs (Section 83), and RSUs (Section 83 + 409A) are taxed differently at every stage. Read the grant agreement and the equity plan.
2. The 409A sets the strike and the bargain element. A defensible 12-month-current 409A is the foundation. Common stock FMV is typically 20% to 40% below preferred due to DLOM and rights gap.
3. AMT can dwarf the regular tax bill at ISO exercise. Always run Form 6251 before exercising more than a small block. AMT credit is recoverable but only when regular tax exceeds AMT in future years.
4. 83(b) within 30 days or never. If you early-exercise, file 83(b) by certified mail within 30 days. No extensions exist.
5. Section 1202 QSBS is the biggest tax benefit in the Code. Up to $10 million (or $15 million post-2025) federal capital gains exclusion after a 5-year hold. Start the clock by exercising early at low FMV.
6. The 90-day post-departure ISO window is real. Plan the cash to exercise years in advance or risk losing the grant entirely if you change jobs.
7. Diversify after the exit. Concentration risk above 20% of net worth in a single illiquid private stock is the most common path to a six-figure regret. Use lockup expiry as the natural moment to diversify.

For employees actively planning a sale of pre-IPO equity, see our companion guides on Stripe tender offers, private company tender offers, QSBS Section 1202 small business stock, the sell-side analyst role in transaction structuring, and choosing the right M and A advisor for an exit. The right preparation in the years before the liquidity event compounds enormously when the event finally arrives.