To determine the fair market value of a startup’s common stock, you commission a Section 409A valuation from a qualified independent appraiser, who estimates the company’s total enterprise value, allocates that value across the different classes of stock, and applies discounts that reflect the illiquidity and limited control attached to common shares. The resulting per-share number becomes the floor for stock option exercise prices and is valid for up to 12 months, or until a material event changes the company’s economics. Setting an exercise price below that number exposes option holders to a 20% penalty tax on top of regular income tax, so getting the process right matters.
What Fair Market Value Actually Means Here
Fair market value is the price at which stock would change hands between a willing buyer and a willing seller, with neither side pressured and both having reasonable knowledge of the relevant facts. That standard comes from federal case law and applies across tax-related valuations. Public companies satisfy it every second the market is open. Private companies have no ticker and no trading volume, so a separate process has to produce the number.
The trap for founders is treating the whole-company valuation from a funding round as the value of a single common share. It isn’t. Venture investors buy preferred stock, which sits ahead of common in the payout order during a sale or liquidation. Preferred shares typically carry a liquidation preference that returns the investor’s money (or a multiple of it) before common holders see a dollar. In a non-participating structure, investors choose between the preference or converting to common at their ownership percentage, whichever pays more. In a participating structure, they take the preference and then share what’s left with the common holders.
The upshot: common stock is worth substantially less per share than preferred stock. In a modest exit, heavy liquidation preferences can leave common holders with very little. Any credible valuation has to capture those structural differences, which is why the FMV of common stock granted to employees lands well below the price investors paid for preferred.
Why the Number Has to Be Defensible
Section 409A of the Internal Revenue Code governs nonqualified deferred compensation, which includes nonqualified stock options. The rule is simple: an option’s exercise price must be set at or above the FMV of the underlying stock on the date of grant.1Office of the Law Revision Counsel. 26 U.S. Code 409A – Inclusion in Gross Income of Deferred Compensation Under Nonqualified Deferred Compensation Plans Set it below FMV and the option is “in the money” at grant, triggering immediate tax consequences even if the recipient never exercises.
Incentive stock options are technically exempt from 409A, but they still require the exercise price to be at least FMV under Section 422. So whether a company grants ISOs or NSOs, it needs a defensible FMV.
The penalties fall on the option holder, not the company. That surprises employees who had no role in pricing the grant. If options are later found to have been underpriced:
- The deferred compensation becomes taxable in the year it vests, even if unexercised.
- An additional 20% tax is imposed on top of regular income tax.1Office of the Law Revision Counsel. 26 U.S. Code 409A – Inclusion in Gross Income of Deferred Compensation Under Nonqualified Deferred Compensation Plans
- Interest runs at the underpayment rate plus one percentage point, calculated from the year the compensation was first deferred or the first year it stopped being subject to a substantial risk of forfeiture.1Office of the Law Revision Counsel. 26 U.S. Code 409A – Inclusion in Gross Income of Deferred Compensation Under Nonqualified Deferred Compensation Plans
Getting Safe Harbor Protection
To insulate the valuation from IRS second-guessing, companies obtain safe harbor protection. Under Treasury regulations, certain valuation methods create a presumption of reasonableness. The Commissioner can only challenge the FMV if the method or its application was “grossly unreasonable,” a high bar.2eCFR. 26 CFR 1.409A-1 – Definitions and Covered Plans
Three methods qualify:
- An independent appraisal by a qualified appraiser, dated no more than 12 months before the grant. This is what most startups use after their first institutional round.2eCFR. 26 CFR 1.409A-1 – Definitions and Covered Plans
- A binding formula that constitutes a nonlapse restriction on the stock, applied consistently for all transfers of that stock class to the issuer or major shareholders.
- The illiquid startup presumption, available to companies less than 10 years old that don’t anticipate a change in control or public offering within 12 months. The valuation still has to be performed by someone with significant knowledge and experience in comparable valuations.
The independent appraisal method dominates because it produces the clearest documentation trail. A board-level determination without an outside appraiser doesn’t qualify for any safe harbor, which means the IRS can challenge the number under a simple reasonableness standard rather than the higher gross-unreasonableness threshold.
How the Appraiser Gets to a Number
The work happens in three phases: estimate the enterprise value, allocate that value across share classes, and apply discounts specific to common stock.
Estimating Enterprise Value
Three standard approaches exist, and most 409A reports blend at least two.
The income approach projects future cash flows and discounts them to present value using a rate that reflects the company’s risk. A high-growth startup with no revenue and heavy burn carries a steep discount rate, which pulls present value down sharply. The appraiser scrutinizes projections for internal consistency and realism. For very early-stage companies with no reliable forecast, the income approach usually plays a supporting role rather than driving the answer.
The market approach values the company against comparable public companies or recent private transactions in the same industry. The appraiser identifies a relevant financial metric (revenue, earnings) and applies trading multiples from the comparable set to the startup. The hard part is finding genuinely comparable companies. A pre-revenue biotech and a SaaS company with recurring revenue live in different valuation universes even if both are “tech startups.”
The asset approach sums the net value of tangible assets. For software or biotech startups this produces an artificially low number, because the real value sits in intellectual property, customer relationships, and people. It matters more for startups with significant physical infrastructure or inventory.
Allocating Value Across Share Classes
Once total enterprise value is set, the appraiser splits it among the different equity classes. This is where common stock drops well below the preferred price, because preferred gets paid first and carries rights common doesn’t.
The Option Pricing Model treats each equity class as a call option on the company’s total value. The preferred stock’s liquidation preference serves as the exercise price, and the model uses inputs like expected time to a liquidity event and the volatility of comparable public companies to compute the value of each class. The OPM suits early-stage companies where the timing and nature of an exit are genuinely uncertain, because it doesn’t require the appraiser to predict a specific outcome. It models a probability distribution across possible outcomes.
The Probability-Weighted Expected Return Method is more hands-on. The appraiser defines specific exit scenarios (IPO at a given valuation, strategic acquisition, continued private operation, dissolution), assigns each a probability, and calculates how proceeds would flow to each class under each scenario. The common stock FMV is the weighted average. PWERM works better for later-stage companies with a clearer line of sight to a specific exit. For a pre-seed company, assigning a probability to an IPO three years out is mostly speculation.
Some appraisers also use a backsolve, which works backward from the price investors paid in the most recent round to derive the total equity value implied by that transaction. The backsolve is particularly useful right after a priced round because it anchors the analysis to an actual arm’s-length negotiation.
Applying Discounts
After allocation produces a per-share value, two discounts typically apply.
The Discount for Lack of Marketability reflects that private stock cannot be sold on a public exchange. Public shares can be sold tomorrow. Startup shares may wait years for a liquidity event, and one is not guaranteed. That illiquidity genuinely reduces what a buyer would pay. The size of the discount varies with expected time to a liquidity event, the presence of any secondary market, and the company’s stage; the appraiser has to justify the specific percentage.
A Discount for Lack of Control may also apply. Common shareholders usually cannot influence major decisions like a sale, merger, or new financing. Preferred shareholders often hold board seats and protective provisions that give them effective veto power. That power gap reduces the value of a minority common position.
These discounts are the main reason a startup can raise a Series A at a $50 million post-money valuation while the 409A sets common at a small fraction of the preferred price. The old rule of thumb that common should be 10–20% of the preferred price is outdated and unreliable. The real ratio depends on the specific capital structure, liquidation preferences, and proximity to a liquidity event.
What Actually Drives the Final Number
Methodologies only work as well as their inputs. The most influential single data point is the price per share from the most recent preferred financing, because it’s an actual negotiated number between sophisticated parties. The appraiser doesn’t take it at face value, though. They adjust for the economic rights attached to the preferred and for the time elapsed since the round closed.
Financial performance carries more weight as the company matures. Revenue growth, gross margins, customer retention, and burn rate all feed the income and market approaches. For pre-revenue companies, qualitative factors dominate: strength of the founding team, size of the addressable market, maturity of the core technology, competitive landscape. These qualitative inputs mostly shape the discount rate and the scenario probabilities, and small shifts there can swing the final number.
Company-produced projections play a central role. An appraiser will push back on hockey-stick projections without supporting evidence, or forecasts that ignore known competitive threats. Defensible projections with clear assumptions produce more reliable valuations and reduce the risk of an IRS challenge.
What to Have Ready, What It Costs, How Long It Takes
Founders can speed things up and improve accuracy by assembling documents before engaging an appraiser. At a minimum, expect requests for:
- Current and historical income statements, balance sheets, and cash flow statements.
- A complete cap table showing all equity classes, option pools, warrants, and convertible instruments.
- Term sheets and stock purchase agreements from recent financing rounds.
- A 12-to-24-month financial forecast with supporting assumptions.
- Pitch deck, major contracts, IP portfolio, and notes on significant recent events.
Cost tracks complexity. Early-stage startups with simple cap tables can expect roughly $2,000 to $5,000, with costs climbing for later-stage companies that carry multiple preferred series, complex waterfalls, or convertible instruments. Timelines usually run two to four weeks from engagement to final report, longer if the company is slow to hand over documents or the appraiser flags issues that need more work.
When You Need a New Valuation
A 409A is valid for 12 months from the date as of which the FMV was measured, not the date the report was delivered. After that, any option grant relying on the expired report falls outside the safe harbor. Calendar the expiration and start the renewal early.2eCFR. 26 CFR 1.409A-1 – Definitions and Covered Plans
The 12-month clock gets overridden by a material event that changes the company’s economic value. The most common trigger is closing a new priced round, because the negotiated share price creates a data point the old valuation didn’t have. Other triggers include a significant acquisition, a major product or revenue milestone, loss of a key customer, resolution of material litigation, or issuance of a patent. If any of these occur, obtain a new valuation before granting more options.2eCFR. 26 CFR 1.409A-1 – Definitions and Covered Plans
Convertible note financings can also trigger an update. A note with a valuation cap implies a specific company valuation, and that cap may be material information the old report didn’t reflect. The safest practice is to treat any financing event as a potential trigger and confirm with your appraiser before the next grant.
If Options Were Priced Below FMV
Mistakes happen. Options can get granted below FMV because of a calculation error, a delayed valuation, or a material event the board didn’t recognize at the time. The IRS provides a narrow correction window under Notice 2008-113.
If the error is caught in the same tax year as the grant, the company can reset the exercise price to at least the FMV on the original grant date, and the option is treated as if it never violated 409A.3Internal Revenue Service. IRS Notice 2008-113 – Guidance on Correcting Certain Failures of Nonqualified Deferred Compensation Plans A second correction window extends through the end of the tax year immediately following the year of grant, though the option holder must include a small amount of income tied to the discount. Outside those windows the options narrow sharply, and the full 409A penalties may apply.
The longer a pricing error goes unaddressed, the harder and more expensive it becomes to fix. A company that suspects an issue should talk to a tax advisor immediately rather than wait to see whether the IRS notices.