You own 20 percent of a profitable family business, and two appraisals land on your desk six months apart. The first, ordered for your father's estate, says your stake is worth $240,000. The second, ordered during a buyout dispute with your siblings, says the same 20 percent is worth $400,000. Nothing about the business changed — same revenue, same customers, same bank balance. Your first instinct is that one of the appraisers made a mistake. Neither of them did. They were answering two different legal questions that happen to share most of the same words: one measured fair market value, the other measured fair value, and the gap between those two standards is doing exactly what it was designed to do.
This confusion costs real money. Owners use an estate-tax appraisal to set a buyout price, book a shareholder settlement at the wrong number, or hand their auditor a valuation built for the IRS and wonder why it gets rejected. The two standards exist for different masters — the tax code and the accounting rulebook — and once you know which master you are serving, the "two different numbers" stop looking like an error and start looking like a map.
The two definitions, side by side
Both standards describe a hypothetical sale. The differences are in who is hypothetically buying, which market they meet in, and what gets subtracted before the answer comes out.
Fair market value is the tax world's standard, and the definition most owners have already met without realizing it. The IRS defines it, in Revenue Ruling 59-60, as the price at which property would change hands between a willing buyer and a willing seller, when neither is under any compulsion to buy or sell and both have reasonable knowledge of the relevant facts. Picture the entire universe of hypothetical buyers and sellers meeting in an open, unrestricted market. That breadth is the point: the IRS wants the price the market at large would set, not the price one special buyer would pay.
Fair value is the accounting world's standard, defined in ASC 820, Fair Value Measurement, as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Notice the narrower cast of characters: not the universe of buyers, but market participants — buyers and sellers in the asset's principal market, or, if there is no principal market, the most advantageous one. The principal market is entity-specific: the market where your company would actually sell that asset, which can differ from company to company for the identical item.
There is also a third character with the same name. Outside financial reporting, "fair value" is a statutory standard in shareholder litigation and divorce cases, defined state by state, and it can differ from both of the above. More on that below — it is where the biggest surprises live.
Four differences that move the number
Definitions are abstract; the adjustments are where dollars appear and disappear. Here are the four wedges between the two standards, ordered from the most mechanical to the most consequential.
1. Which market counts
Fair market value looks outward at an open market. Fair value looks at your principal market. For a publicly traded stock these are the same place, which is why the distinction feels academic until it isn't. For everything else — a used delivery van, a patent, a minority stake in a private company — the principal market is the specific market where you would transact, and ASC 820 ranks the evidence in a three-level hierarchy: quoted prices for identical assets get the most weight (Level 1), observable prices for comparable assets get less (Level 2), and your own models and assumptions get the least (Level 3). An auditor evaluating your estimate will ask which level your inputs sit on before asking anything else.
2. Exit price, not entry price
Fair value is explicitly an exit price: what you would receive to sell, not what you paid to buy. That framing matters because buying and selling prices diverge the moment transaction costs, installation, or customization enter the picture. The transaction must also be orderly — exposed to the market for its usual marketing period, not a fire sale. A forced liquidation price is not fair value under ASC 820, just as a distressed sale is not fair market value under the willing-buyer test. If someone pressures you to book an asset at what a liquidator offered over the phone, both standards agree the answer is no.
3. The discounts: where 40 percent goes missing
This is the wedge that explains the $240,000 versus $400,000 puzzle at the top. A minority stake in a private company is worth less, per share, than its slice of the whole — the holder cannot force dividends, block a sale, or sell the shares on any exchange. Valuators quantify that reality with two discounts:
- The discount for lack of control (DLOC), reflecting that a minority holder cannot direct the company. Typical magnitudes run 15 to 25 percent.
- The discount for lack of marketability (DLOM), reflecting that there is no ready market to convert the interest to cash. Typical magnitudes run 15 to 35 percent, sometimes more.
Under fair market value, both discounts normally apply: the hypothetical willing buyer of your 20 percent would absolutely pay less for a non-controlling, unsellable stake, and the IRS expects the appraisal to say so. Under statutory fair value in shareholder disputes, many states bar the minority discount outright — the logic being that the majority should not benefit from a discount created by its own control — and some bar the marketability discount too. The applicable rule varies by state, which is why a buyout valuation must name the jurisdiction whose law it follows.
Run the arithmetic on a $2,000,000 business where your 20 percent is worth $400,000 pro-rata. Apply a 20 percent DLOC and the value drops to $320,000; apply a 25 percent DLOM on top and you land at $240,000. Same company, same stake — and the only thing that changed is which standard's discounts were allowed. Neither number is wrong. Each answers the question its standard asks.
4. Investment value is neither of them
A buyer who will pay extra because your customer list completes their product line is offering investment value — what the business is worth to that specific buyer, synergies included. Fair market value deliberately excludes the special buyer; it prices the interest for the market at large. Owners who anchor on a strategic acquirer's offer and then feel cheated by a lower FMV appraisal are comparing a price to a standard. If you ever receive an offer far above a recent appraisal, congratulations — but do not book the difference as an error by the appraiser.
When each standard shows up in your life
You do not need to memorize ASC paragraphs. You need to recognize which standard a situation demands, because bringing the wrong one is the single most common mistake.
Fair market value governs tax and transactions. You meet it when you sell the business or a stake in it, when shares transfer through an estate or a gift, when you donate appreciated property to charity and claim a deduction, when you contribute property you already own into your own company, when a buy-sell agreement sets its formula price, and when a startup prices stock options under Section 409A. In each case the question is some version of "what would the open market pay," and the appraisal should say FMV on its face.
Fair value governs the financial statements. Under GAAP you meet it when reporting share-based compensation, when allocating a purchase price across goodwill and identifiable intangibles after an acquisition, and when testing long-lived assets and intangibles for impairment. Here the question is "what exit price would market participants agree in our principal market," and the answer often comes from a credentialed valuator independent of your audit firm — management makes the estimate, the auditor evaluates whether it looks reasonable, and neither side grades its own homework.
Statutory fair value governs the courtroom. Shareholder oppression and dissenting-shareholder appraisal cases use "fair value" as their state statutes define it, and divorce courts use whatever standard their jurisdiction prescribes. These definitions borrow the accounting term's name while answering an equitable question — what is a fair buyout price given the parties' conduct — so discounts allowed everywhere else may be barred here. If you are ever on either side of a forced buyout, the first question for your attorney is not "what is it worth" but "which standard does this court apply, and which discounts does it allow."
How the two numbers hit your books
Valuation standards feel theoretical until a transaction forces you to record one. The most common FMV moment in a small business is an in-kind owner contribution: you transfer a van, a laptop fleet, or a parcel of equipment you already owned into the company. You did not pay the company cash, so there is no purchase price to record — tax law books the contribution at fair market value, supported by dealer quotes or a short appraisal kept with your records.
Suppose you contribute a used cargo van appraised at $18,500. If you keep your books in Beancount, the contribution is one transaction — debit the asset at FMV, credit your equity contribution the same amount. The Beancount documentation covers transaction syntax in full; here is the contribution, plus the year-end impairment write-down GAAP would require if the van's exit price in your principal market later fell to $14,000:
2026-11-03 * "Owner contributes cargo van at appraised FMV"
Assets:Vehicles:Cargo-Van 18500.00 USD
Equity:Owner-Contributions -18500.00 USD
2026-12-31 * "Impair cargo van to fair value in principal market"
Expenses:Impairment:Loss 4500.00 USD
Assets:Vehicles:Cargo-Van -4500.00 USDBoth entries record a "value," but they answer different questions six weeks apart: the November entry asks what the open market would pay (FMV, for the tax basis of your contribution), while the December entry asks what exit price your principal market offers (fair value, for the GAAP carrying amount). Filing the $18,500 appraisal with the November entry is what lets you defend the equity credit if the IRS ever asks why a van with no purchase invoice sits on the balance sheet.
Mistakes that mix the standards
Most valuation errors are not arithmetic. They are category errors — the right math under the wrong standard.
Handing your auditor a tax appraisal. An estate-tax FMV report bakes in DLOM and DLOC and prices the interest for the universe of buyers. None of that belongs in a GAAP fair-value measurement, which wants an undiscounted exit price from your principal market with Level 1 through 3 evidence ranked. The auditor will reject it, the impairment test will be redone, and you will pay for two valuations instead of one.
Applying discounts a court would bar. Discounting a minority stake 40 percent in a buyout governed by a fair-value statute that disallows DLOC does not just underpay the departing holder — it hands them an argument that the valuation ignored controlling law. Discount practice follows the forum, not the appraiser's habits.
Booking a strategic offer as FMV. If one acquirer offers a 30 percent premium for synergies, that premium is investment value. Recording your equity at the offer price overstates FMV for gift, estate, and 409A purposes and understates the discount a hypothetical market buyer would demand.
Letting the valuation go stale. Both standards are measured at a date — the measurement date under ASC 820, the transfer date under the tax rules. A twelve-month-old appraisal is a history lesson, not a measurement. Major contracts, lost customers, rate moves, and new debt all age a valuation faster than the calendar suggests.
Your last useful step
Pull the most recent valuation anywhere in your files — an estate appraisal, a 409A report, the formula page of your buy-sell agreement — and find the sentence that names its standard of value. If it says fair market value, check that any minority or marketability discounts are stated separately from the pro-rata number, so you can see what the undiscounted value was. If it says fair value, check whether it names ASC 820 or a state statute, because those two "fair values" allow different discounts. And if no sentence names a standard at all, you do not have a valuation — you have an opinion with formatting. Get the standard in writing before the number matters, because the day it matters is the day someone else's expert explains, correctly, that your number answers the wrong question.
