409A Valuations and Incentive Stock Options (ISOs) vs. Nonqualified Stock Options (NSOs)
Author: Redwood Valuation Content Team
Published: July 29, 2026
A 409A valuation does more than support a private company’s option strike price. For stock options, the valuation helps document whether the exercise price was at least fair market value on the grant date. That conclusion matters for nonqualified stock options because it determines whether the option can stay outside Section 409A. It also matters for incentive stock options because fair market value is one of the qualification requirements under Section 422.
The two regimes are related, though they operate on different tracks. An incentive stock option (ISO) is governed by IRC Section 422. A nonqualified stock option is generally taxed under the ordinary Section 83 framework when exercised (assuming it is not subject to Section 409A). Section 409A is a separate deferred compensation regime that can apply when an option is granted at a discount or includes an impermissible deferral feature. When a valuation is not defensible, an option intended to be an ISO may raise both ISO qualification and Section 409A questions.
The sections below explain how the fair market value requirement works for ISOs and NSOs. They also show where the 409A valuation fits into each option type and what companies should watch when granting options to employees, advisors, directors, or other service providers.
The 409A Rule for Stock Options
A nonstatutory stock option generally falls outside Section 409A if four conditions are met: the exercise price may never be less than the fair market value of the underlying service recipient stock on the grant date; the number of shares is fixed on the original grant date; the option is taxed under Section 83; and the option does not include another feature that permits deferred compensation. If the exercise price is or can become less than fair market value on the grant date, the option generally provides for deferred compensation under Section 409A (Treas. Reg. Section 1.409A-1(b)(5)(i)).
That rule is why the valuation work matters. A private company usually does not have a quoted market price for common stock. The company has to support fair market value through a reasonable valuation method or one of the regulatory safe harbor methods discussed below.
The fair market value standard for Section 409A is a tax standard. It is commonly described through the willing-buyer/willing-seller framework: the price at which property would change hands between a willing buyer and a willing seller, neither under compulsion and both having reasonable knowledge of relevant facts. Financial reporting uses a different standard under ASC 820, which is based on fair value and market participant assumptions. The two concepts overlap in some ways but are not interchangeable.
That makes two terms worth keeping separate:
Section 409A uses fair market value (FMV), a tax concept used to support the option exercise price.
Financial reporting uses fair value, an accounting concept under GAAP. In a 409A stock-option context, “fair value” is usually the wrong term unless the article is separately discussing financial reporting.
For private company stock, Treasury regulations look to the reasonable application of a reasonable valuation method. Relevant factors can include the company’s tangible and intangible assets, anticipated cash flows, market values of comparable companies, recent arm’s-length transactions, control premiums, discounts for lack of marketability, and other facts known as of the valuation date. A valuation can lose its support under the regulations if it ignores material information or relies on an old value after material facts have changed.
ISO vs. NSO: Key Differences
ISOs and NSOs are often discussed together because both are stock options. For tax and valuation purposes, they work differently. The table below shows where the two diverge.
ISO vs. NSO: Key Differences
| ISO | NSO | |
|---|---|---|
| Governing statute | IRC Section 422 | IRC Section 83 |
| Who can receive | Employees only | Employees, contractors, advisors, directors, and other service providers |
| Exercise price requirement | Exercise price must be at least FMV at grant to satisfy Section 422(b)(4), subject to the Section 422(c)(1) good-faith valuation rule | Exercise price generally must be at least FMV at grant to avoid Section 409A deferred compensation treatment |
| Ordinary income at grant | No | Usually none, absent a readily ascertainable FMV |
| Ordinary income at exercise | No regular taxable income if ISO requirements are satisfied; AMT may apply | Yes; the spread is ordinary income under Section 83(a) |
| Withholding at exercise | No income tax withholding or FICA/FUTA on exercise, including on a later disqualifying disposition (though the income is reportable) | Yes; subject to income tax withholding and employment taxes for employees |
| $100K annual vesting limit | Yes; excess is treated as NSO under Section 422(d) | No |
A qualifying ISO produces no ordinary income at exercise for regular federal income tax purposes under Section 421. The spread between the fair market value at exercise and the exercise price can still be an alternative minimum tax (AMT) adjustment under IRC Section 56(b)(3). If the employee holds the shares for more than two years from the grant date and more than one year from the exercise date, gain on sale can qualify for long-term capital gain treatment. A sale before those holding periods is a disqualifying disposition and generally creates ordinary compensation income.
An NSO works differently. At exercise, the spread is ordinary income under Section 83(a). That income is generally subject to withholding and employment taxes for employees. The company typically receives a corresponding deduction under Section 83(h), subject to the usual limits and reporting requirements. Any later appreciation above the fair market value at exercise is capital gain, long-term if the shares are held for more than one year after exercise.
The $100,000 ISO limit is another place where the grant-date valuation matters. Under Section 422(d), ISOs that first become exercisable in a calendar year are counted using the fair market value of the underlying stock determined at the time of grant. To the extent the aggregate value first exercisable in a year exceeds $100,000, the excess portion is treated as an NSO. That conversion does not itself create a Section 409A problem if the exercise price was at least fair market value at grant. The excess portion still needs to be analyzed under the NSO rules.
How 409A Valuations Interact with ISOs
ISOs that satisfy Section 422 are excluded from Section 409A. Treasury regulations state that the grant of an incentive stock option described in Section 422 does not constitute a deferral of compensation. That exclusion depends on the option actually qualifying as an ISO.
The valuation connection comes from Section 422(b)(4), which requires the option price to be at least the fair market value of the stock at the time the option is granted. In practice, the 409A valuation is often the main document supporting that conclusion for a private company. A current and well-documented valuation gives the company a much stronger record that the ISO exercise price was set correctly, especially if the valuation falls within a properly applied safe harbor.
There is an important nuance here. Section 422(c)(1) contains a good-faith valuation rule for ISOs. Under that rule, an option is not treated as failing the Section 422(b)(4) fair market value requirement merely because the company’s good-faith attempt to determine value later proves wrong. A later valuation dispute therefore does not automatically destroy ISO treatment. The rule is not a substitute for real valuation support. If the company cannot show a good-faith attempt to determine fair market value, the ISO position becomes harder to defend.
When the fair market value support fails, the analysis changes. A purported ISO that does not qualify under Section 422 may need to be treated as an NSO. If the exercise price was below the true fair market value at grant, the option can then raise Section 409A issues as a discounted nonstatutory stock option.
The risk sequence looks like this:
The company grants an option intended to qualify as an ISO.
The strike price is set using an FMV determination that later proves unsupported, stale, or not made in good faith.
If the strike price was below true FMV and the good-faith ISO rule does not protect the grant, the option may fail Section 422(b)(4).
The option must then be analyzed as an NSO.
If the resulting NSO was granted below FMV, it generally provides for deferred compensation under Section 409A.
At that point, a valuation problem can become more than an ISO-labeling issue. The company may have expected ISO treatment. The employee may instead face ordinary income, withholding and reporting complications, and potential Section 409A consequences depending on the facts.
Other Section 422 requirements still matter. An ISO must be granted under a written plan approved by shareholders. The option term generally cannot exceed 10 years. Special rules apply to 10-percent shareholders, and the optionee must satisfy the employee-status requirements. For valuation purposes, the fair market value requirement at grant is the one that matters most.
How 409A Valuations Interact with NSOs
For NSOs, the Section 409A issue is more direct. An NSO granted with an exercise price at or above fair market value generally does not provide for deferred compensation, assuming the other regulatory conditions are met. The option can then operate like a typical private-company NSO: no ordinary income at grant for a typical option without readily ascertainable value, ordinary income on the spread at exercise, and capital gain or loss after exercise based on the later sale price.
A discounted NSO is different. If the option is granted with an exercise price below fair market value, it generally becomes deferred compensation under Section 409A. In theory, a deferred compensation arrangement can comply with Section 409A. In practice, a typical NSO is not designed that way because the holder usually controls the timing of exercise. That flexibility often conflicts with Section 409A’s timing and payment rules.
Side by side, the practical difference looks like this:
NSO Grant Price vs. FMV: Section 409A Outcomes
| NSO Grant Relative to FMV | Section 409A Status | Tax Consequences |
|---|---|---|
| At or above FMV at grant | Generally not deferred compensation if the regulatory requirements are satisfied | Ordinary income on the spread when exercised; withholding and employment taxes generally apply for employees |
| Below FMV at grant | Generally deferred compensation under Section 409A | Income inclusion under Section 409A to the extent vested and not previously included, plus the 20% additional tax and premium interest if the arrangement does not comply |
That is why the same valuation conclusion matters for both option types. With an ISO, FMV supports Section 422 qualification. With an NSO, FMV supports the Section 409A exemption. In both cases, the company needs to be able to show why the grant-date exercise price was not below fair market value.
When the Double-Failure Risk Applies
The double-failure risk is real. It should be stated carefully because a valuation issue does not automatically convert every ISO into an NSO and trigger Section 409A. The better way to frame the risk is that an unsupported or unreasonable FMV determination can undermine both the intended ISO treatment and the Section 409A position if the option was actually granted at a discount.
For an option intended as an ISO, the failure pattern usually has three parts:
The company used a valuation that did not reasonably support the grant-date FMV.
The exercise price was below true FMV at grant, and the company cannot rely on the Section 422(c)(1) good-faith valuation rule.
The option fails ISO treatment and must be analyzed as an NSO; because the strike was below FMV, the NSO generally falls within Section 409A.
At that point, the service provider can face income inclusion under Section 409A to the extent the deferred amount is vested and not previously included in income. The service provider can also face a 20% additional income tax and premium interest calculated by reference to the year the compensation was first deferred or, if later, the first year it was not subject to a substantial risk of forfeiture. Those are employee- or service-provider-level tax consequences, not a 20% tax imposed directly on the company.
The company’s exposure is still significant. It may have withholding and reporting obligations. It may face contractual gross-up claims if the option agreement or employment agreement provides one. It may also have to manage legal fees, audit costs, accounting cleanup, and employee-relations damage. For key hires, the practical cost of a valuation mistake can exceed the tax mechanics.
Sutardja v. United States (Fed. Cl. 2013) is often cited in this area because the Court of Federal Claims accepted the IRS position that discounted stock options may be subject to Section 409A. The case is a useful reminder that discounted options are not merely a pricing issue. They can become deferred compensation instruments with a tax regime that most option plans were not designed to satisfy.
Correction may be possible in some cases, though it is a conditional path rather than a guaranteed fix. IRS Notice 2008-113 provides relief for certain operational failures, including specified corrections of exercise prices for otherwise excluded stock rights. The correction procedures have timing requirements, service-provider limitations, and reporting conditions. They should be treated as a narrow remediation path, not as a substitute for getting the valuation right before grants are approved.
Safe Harbor Methods for Getting FMV Right
Treasury regulations give private companies three valuation safe harbors for service recipient stock that is not readily tradable on an established securities market. If a safe harbor is used correctly, the valuation is presumed reasonable. The IRS can rebut that presumption only by showing that the valuation method or its application was grossly unreasonable. Outside the safe harbors, the company is left with a broader facts-and-circumstances reasonableness standard.
Independent appraisal. The most common safe harbor in practice is an independent appraisal with a valuation date no more than 12 months before the relevant option grant. This is the standard 409A valuation report that most venture-backed and growth-stage companies use when granting stock options. It is generally the cleanest approach when the company expects investor diligence, auditor review, or a material grant program.
Formula valuation. A formula-based valuation may qualify if the formula would be treated as fair market value under the nonlapse-restriction rules of Section 83 and is used consistently for all transfers of that class of stock (or a substantially similar class), whether compensatory or not, including transfers to the issuer and to 10% or greater shareholders. This method is less common for venture-backed start-ups because it is hard to maintain consistently across all required transactions.
Illiquid start-up valuation. A qualifying start-up can use a written valuation made reasonably and in good faith by a qualified person with significant knowledge, experience, education, or training in business valuation or a related field. The company generally must not have a material trade or business that it or a predecessor has conducted for 10 years or more, and it must not have publicly traded equity securities. It also must not have a change in control reasonably anticipated within 90 days or a public offering reasonably anticipated within 180 days. The stock also cannot be subject to a put, call, or similar obligation, with limited exceptions for rights of first refusal and certain repurchase rights. Whether the person performing the valuation has the required qualifications is a facts-and-circumstances question. In practice, this standard is often met by individuals with substantial relevant experience, such as five or more years in business valuation or appraisal, financial accounting, investment banking, private equity, secured lending, or other comparable experience in the line of business or industry.
The illiquid start-up method is often misunderstood. It can be performed internally if the company and the person performing the valuation meet the regulatory requirements. The question is not simply whether the company hired a third-party firm. The question is whether the company qualifies, whether the valuation is written and well supported, and whether the person performing it is someone a reasonable person would rely on for valuation advice.
The safe harbor has limits. It does not make a stale or incomplete valuation immune from challenge. The regulations state that using a prior valuation is not reasonable if later information materially affecting value is available or if the valuation date is more than 12 months before the date for which the value is being used. Material events can shorten the useful life of a valuation even when the report is less than 12 months old.
Penalties and Who Bears Them
Section 409A penalties fall on the person who received the option (the employee, contractor, or advisor) who holds the noncompliant deferred compensation rather than directly on the company. The main consequences are income inclusion for vested amounts not previously included in income, a 20% additional income tax, and premium interest. The 20% amount is an additional income tax under Section 409A, not an excise tax.
For employees, income includible under Section 409A is generally reported on Form W-2 in Box 1 and Box 12 using code Z. Employers must withhold federal income tax on amounts includible in gross income under Section 409A. They do not withhold the additional Section 409A tax or premium interest. For nonemployees, current Form 1099-MISC instructions distinguish Section 409A deferrals from nonqualified deferred compensation income; Box 15 is used for income under an NQDC plan that does not meet Section 409A requirements. Reporting mechanics can change, so companies should check the current IRS instructions when a correction or reporting obligation arises.
The company does not owe the 20% additional tax directly. It can still have several forms of exposure:
Withholding and reporting obligations on amounts included under Section 409A
Gross-up obligations if the relevant agreement requires the company to make the service provider whole
Legal, audit, payroll, and accounting costs associated with a Section 409A failure
Employee-relations damage when option holders face unexpected tax liability
Practical Compliance Considerations
A 409A valuation needs to support fair market value as of the option grant date. The common shorthand that a 409A valuation is “good for 12 months” is incomplete. The regulations allow reliance on a prior valuation only if it remains reasonable in light of the facts available at the grant date. A financing, major customer win, material revenue change, significant litigation development, acquisition offer, or similar value-changing event may require a refresh before the 12-month period expires.
The grant date should also be handled carefully. For Section 409A purposes, the grant date is generally the date the company completes the corporate action establishing the option with all material terms, including the recipient, number of shares, class of stock, and exercise price. Later paperwork should match the board approval rather than create uncertainty about when the grant was actually made.
Companies should consider refreshing or revisiting a 409A valuation when:
A new financing round closes, or term sheet pricing materially changes the company’s value expectations
A material business event occurs, such as a major contract, litigation development, acquisition indication, significant revenue change, or material product milestone
The prior valuation date is approaching 12 months old
The company is preparing a broad grant program, an executive grant, or a contractor/advisor grant where the option terms may receive later scrutiny
The company is approaching a possible change in control or public offering timeline that may affect safe harbor eligibility
For early-stage companies considering the illiquid start-up safe harbor, the key question is whether the company and the valuation provider satisfy the regulatory requirements. A board judgment call is not the same thing as a written valuation. The company should be able to show how the value was determined, what information was considered, why the method was reasonable, and why the person performing the valuation was qualified.
Working With a Valuation Firm
A defensible 409A valuation supports more than an option strike price. It helps preserve intended ISO treatment and keeps at-FMV NSOs outside Section 409A. It also gives the company a record it can use in diligence, audit, payroll, and tax-review settings. The right valuation process depends on the company’s stage, capitalization, grant timing, financing history, and expected transactions.
Redwood works with companies at every stage, from early start-ups evaluating whether an illiquid start-up safe harbor approach may fit to growth-stage companies that need independent appraisal support. If you have questions about which valuation approach fits your option grant timeline, contact Redwood Valuation to talk through the facts before grants are approved.
Frequently Asked Questions
Do ISOs need a 409A valuation if they are excluded from Section 409A?
A qualifying ISO is excluded from Section 409A. A 409A valuation is still important because Section 422 requires the exercise price to be at least fair market value at grant. For a private company, the 409A valuation is usually the central document supporting that grant-date FMV conclusion.
Does every ISO valuation error automatically convert the ISO into an NSO?
No. Section 422(c)(1) includes a good-faith valuation rule for attempts to meet the Section 422(b)(4) FMV requirement. A later dispute over value does not automatically destroy ISO treatment. The risk increases when the valuation was stale, unsupported, or not made in good faith and the strike price was actually below fair market value at grant.
Who pays the Section 409A penalty if options were granted below FMV?
The person who received the option (the employee, contractor, or advisor) pays the Section 409A tax consequences: income tax and premium interest. The company does not pay the 20% additional tax directly. It may still have withholding, reporting, gross-up, legal, audit, and employee-relations exposure.
Is a 409A valuation legally valid for exactly 12 months?
Not exactly. The 12-month period is an outer boundary for using a prior valuation under the regulations, not a guarantee that the value remains current for the full period. If material information becomes available after the valuation date and before the grant date, the prior valuation may no longer be reasonable.
Can a start-up do an internal 409A valuation?
A qualifying start-up may be able to use the illiquid start-up safe harbor, which allows a written valuation by a qualified person with significant knowledge, experience, education, or training in business valuation or a related field. The company must satisfy the start-up conditions. The valuation must be written, reasonable, made in good faith, and based on the relevant valuation factors.
What happens when ISO vesting exceeds $100,000 in a year?
The portion of ISOs first exercisable in a calendar year above the $100,000 limit is treated as NSOs under Section 422(d), measured using the fair market value of the stock at grant. That conversion does not create a Section 409A issue by itself if the exercise price was at least FMV at grant. The converted portion should still be analyzed under the NSO rules.