Fair Market Value: IRS Definition and How It Works

Fair market value is the price a property would sell for on the open market between a willing buyer and a willing seller, with neither under any compulsion to act and both having reasonable knowledge of the relevant facts. The IRS, the courts, and financial regulators all use this same definition to measure what something is worth for tax reporting, estate settlement, insurance claims, divorce, and corporate deals. Getting the number right matters: the IRS can impose penalties of 20% to 40% of the resulting tax underpayment when a reported value misses by a wide enough margin.

What the Definition Actually Requires

The IRS defines fair market value as “the price that property would sell for on the open market” between “a willing buyer and a willing seller, with neither being required to act, and both having reasonable knowledge of the relevant facts.”¹ The Treasury regulations governing estate tax use nearly identical language: FMV is “the price at which the property would change hands between a willing buyer and a willing seller, neither being under any compulsion to buy or to sell.”²

Three things about the definition trip people up. The transaction is hypothetical, not what someone actually paid in a rushed sale, a family deal, or a foreclosure. Both parties are assumed to know the relevant facts, so you can’t argue that a lower price reflects FMV because the buyer overlooked mineral rights. And “open market” means unrestricted; the estate tax regulation specifically says FMV “is not to be determined by a forced sale price.”²

Highest and Best Use

Appraisers determine FMV by assuming the asset is put to its highest and best use at the time of valuation. That use must be physically possible, legally allowed under zoning and building codes, financially feasible based on projected returns, and maximally productive compared to other qualifying uses. A vacant lot zoned for commercial development may be valued as the site of a retail building rather than the community garden currently on it. A property that could legally become a 20-story hotel but would lose money as one fails the financial feasibility test, so the appraiser would look to a different use.

The Right Market

The estate tax regulation adds an important wrinkle: FMV should reflect the market where the item is most commonly sold to the public. A car in a decedent’s estate is valued at what a buyer would pay at a dealership, not the wholesale price a dealer would pay at auction.² The same rule applies to household goods, collectibles, and other personal property.

How Appraisers Actually Set the Number

Professional appraisers use three recognized methods. Formal appraisals usually apply at least two and weigh the results. Which method carries the most weight depends on the type of asset and the data available.

Market Approach

The market approach estimates value from what comparable assets recently sold for in arm’s-length transactions. Real estate appraisers call these comps. The appraiser finds sales of similar properties and adjusts for differences in size, age, location, condition, and financing terms. If a comparable home sold with below-market seller financing, the appraiser adjusts downward because the recorded price was inflated by the concession. This approach works best when reliable, recent sales data exists, and becomes less useful for specialized assets like custom manufacturing facilities or one-of-a-kind artwork.

Cost Approach

The cost approach starts from the idea that a reasonable buyer wouldn’t pay more than it would cost to build an equivalent from scratch. The appraiser estimates replacement cost using current materials and construction, then subtracts depreciation for physical wear, design flaws that leave the asset less functional than modern alternatives, and external economic factors like neighborhood decline. This method is most useful for newer construction, special-purpose buildings like churches or schools, and assets that rarely trade on the open market.

Income Approach

The income approach converts an asset’s expected future earnings into a present-day figure. Appraisers favor it for rental properties, operating businesses, and royalty streams. The most common technique is discounted cash flow analysis, which projects net income over a set period and discounts it back using a rate that reflects the risk of receiving those cash flows. For properties with stable income, appraisers sometimes use direct capitalization, dividing one year’s expected net operating income by a capitalization rate from comparable investment sales. A building producing $100,000 in net income in a market with a 5% cap rate has an indicated value of $2 million.

Fair Market Value on Your Tax Return

FMV anchors several federal tax calculations. The IRS requires it whenever you report inherited assets, make a gift, donate property to charity, or dispose of digital assets.

Estate Tax and Stepped-Up Basis

Every asset in a decedent’s gross estate must be valued at FMV as of the date of death.² The executor may instead elect the alternate valuation date, which values assets six months after death (or on the date of any earlier sale or distribution). The election is only available if it decreases both the total value of the gross estate and the combined estate and generation-skipping transfer tax.³

For closely held businesses, partnership interests, and other assets that don’t trade on a public exchange, the estate generally needs a professional appraisal. Appraisers commonly apply discounts for lack of marketability and lack of control when valuing minority interests, reflecting the real difficulty of selling a non-controlling stake in a private company.

When you inherit property, your cost basis becomes the FMV on the date of death (or the alternate valuation date, if elected).⁴ This step-up wipes out unrealized capital gains that accrued during the decedent’s lifetime. If your parent bought stock for $10,000 and it was worth $200,000 at death, your basis is $200,000. Sell it the next month for $200,000 and you owe no capital gains tax.

Gifts

Gifted property works differently. The recipient takes the donor’s original basis, which can create a much larger future tax bill. There’s a wrinkle for losses: if the donor’s basis exceeds the FMV at the time of the gift, the recipient must use the lower FMV as the basis when calculating a loss on a later sale.⁵ That creates a no-man’s-land where a sale price between the donor’s basis and the gift-date FMV produces neither a gain nor a loss.

Charitable Contributions

Non-cash charitable donations are generally deductible at FMV. When you donate property worth more than $5,000, you must obtain a qualified appraisal and file Form 8283 with your return.¹ The appraisal must be signed by both the appraiser and the receiving charity, and the charity takes on an obligation to report any sale of the donated property within three years.

An important exception applies to tangible personal property. If you donate physical items and the charity puts them to a use unrelated to its exempt purpose, your deduction is reduced by the amount of any long-term capital gain that would have been realized on a sale. In practice, that limits your deduction to your cost basis rather than the full FMV.⁶ Donating a painting to a hospital that hangs it in a waiting room (related to its mission) preserves the full deduction; donating it to a hospital that immediately sells it may not.

Cryptocurrency and Digital Assets

The IRS treats cryptocurrency and other digital assets as property, so every taxable event requires you to document FMV in U.S. dollars.⁷ For transactions on a cryptocurrency exchange, FMV is the dollar amount recorded by the exchange. If the transaction occurs off-chain through the exchange, FMV is the trading price at the date and time the transaction would have been recorded on the blockchain had it been on-chain.⁸

Peer-to-peer transactions are trickier. The IRS will accept values from a cryptocurrency or blockchain explorer that analyzes worldwide indices and calculates the price at an exact date and time.⁸ Without an explorer, you bear the burden of proving that whatever value you reported accurately represents FMV. For non-fungible tokens with no active trading market, establishing FMV may require comparable sales of similar tokens or a professional appraisal.

Fair Market Value Outside the Tax Return

Home Purchases and Property Taxes

When you apply for a mortgage, the lender orders an independent appraisal to confirm the home’s FMV supports the loan amount. If the appraisal comes in below the agreed purchase price, the lender may refuse to finance the difference, leaving you to renegotiate, pay the gap in cash, or walk away. Real estate agents also prepare a comparative market analysis to help set a listing price, but a CMA is informal and can’t substitute for a licensed appraisal when a lender or the IRS needs documentation.

Local governments calculate property tax bills based on an assessed value that’s supposed to reflect FMV, or a percentage of it. County assessors use mass appraisal models that estimate values for thousands of properties at once, relying on public records like square footage, lot size, year built, and recent neighborhood sales. Assessed value can diverge from true FMV because assessment cycles lag market shifts, homestead caps limit annual increases, and mass appraisal lacks the precision of a property-specific inspection. If your assessment looks too high, most jurisdictions offer an appeal process that typically runs from an informal review with the assessor, to a petition to a local board of review, to an appeal to a state board or court. Deadlines are strict and vary by jurisdiction.

Business Deals and Shareholder Disputes

When one company acquires another, the purchase price must be allocated across the acquired company’s assets and liabilities at their individual fair values. Intangible assets like customer relationships, trade names, patents, and technology get identified and valued separately, then amortized over their useful lives. The leftover purchase price that can’t be assigned to identifiable assets becomes goodwill.

When a corporation merges or makes another fundamental change, minority shareholders who object often have the right to demand a buyout at FMV rather than accept the deal terms. This right, sometimes called dissenters’ or appraisal rights, exists in some form in every state, and the valuation is typically fixed as of the day before the transaction is announced. Many closely held businesses head off these disputes with buy-sell agreements that specify how shares will be valued when an owner dies, retires, or becomes disabled, either through a periodic FMV appraisal or a formula tied to earnings or book value.

Divorce

A majority of states use FMV as the standard for valuing marital assets during property division. The family home, retirement accounts, a private business, and vehicles all need assigned values for the court to divide the estate equitably. Business valuation is particularly contentious: the owner-spouse may argue the business has little value without their personal involvement, while the other spouse pushes for a higher figure that includes built-up goodwill. Getting an independent appraisal early tends to prevent the most expensive disputes.

Insurance Claims

Property insurance policies settle losses using one of two standards. Actual cash value is essentially replacement cost minus depreciation for age, wear, and obsolescence. A roof with a 30-year lifespan that’s 15 years old might be depreciated by half, leaving you with a payout far below what it costs to install a new one. Replacement cost coverage pays to replace or repair without a depreciation deduction, provided you actually complete the repairs within the policy’s required timeframe. Your policy specifies which standard applies; where it uses ACV, the FMV concept is directly relevant because ACV approximates what the damaged property would have sold for in its pre-loss condition.

Eminent Domain

The Fifth Amendment requires just compensation when the government takes private property for public use.⁹ Courts universally interpret just compensation to mean the property’s FMV.¹⁰ In a partial taking, where the government acquires only a portion of a larger parcel, compensation includes both the FMV of the land taken and any reduction in value to the remaining property. These severance damages might reflect lost access, increased noise, or a change in the property’s most productive use. The owner bears the burden of proving the remaining property lost value as a direct result of the taking.

What Fair Market Value Is Not

Several other valuation concepts sound similar to FMV but produce very different numbers, and using the wrong one in a tax filing or legal proceeding can be costly.

Book value is an accounting figure: total assets minus total liabilities on a company’s balance sheet. Because it’s based on historical cost and depreciation schedules rather than current market conditions, book value often diverges sharply from FMV. A company with minimal tangible assets but a powerful brand and loyal customer base will show a low book value and a much higher FMV.

Investment value measures what an asset is worth to a specific buyer based on that buyer’s unique circumstances, like anticipated synergies, tax position, or financing terms. A competitor acquiring a rival’s customer list may value it far higher than the open market would. FMV is objective and buyer-neutral; investment value is inherently subjective.

Liquidation value is what you’d get by selling assets quickly, often under time pressure. It assumes a limited marketing period and a seller who needs to dispose of assets fast. Because FMV assumes a reasonable marketing period and a seller acting without duress, liquidation value is almost always lower.

Penalties for Getting the Number Wrong

Overvaluing a charitable donation or undervaluing an estate asset doesn’t just trigger an audit. The IRS imposes a 20% penalty on the tax underpayment when the claimed value is 150% or more of the correct amount, a threshold called a substantial valuation misstatement.¹¹ The penalty doubles to 40% for a gross valuation misstatement.¹² In either case, the penalty only kicks in if the resulting tax underpayment exceeds $5,000 ($10,000 for C corporations).

Appraisers face their own penalties. An appraiser whose valuation results in a substantial or gross misstatement can be penalized for the greater of 10% of the tax underpayment caused by the misstatement or $1,000, capped at 125% of the gross income the appraiser received for the engagement. The appraiser can avoid the penalty by establishing that the reported value was “more likely than not” correct.¹

For taxpayers, the primary defense against valuation penalties is showing reasonable cause and good faith. The IRS considers your efforts to report the correct value, the complexity of the issue, your experience, and whether you relied on a competent tax advisor who had all the relevant information.¹³

What Counts as a Qualified Appraisal

The IRS doesn’t accept just any estimate. For charitable donations exceeding $5,000 and many estate filings, a qualified appraisal from a qualified appraiser is required, and both terms have specific regulatory definitions.

A qualified appraiser must have verifiable education and experience in valuing the specific type of property at issue. The IRS accepts two paths: completing professional or college-level coursework in valuing the property type combined with at least two years of relevant experience, or holding a recognized appraiser designation from a professional organization based on demonstrated competency.¹⁴ The appraiser must declare in the report that their education and experience qualify them for the specific property type being valued.

A qualified appraisal must include a detailed description of the property, its condition (for real or tangible personal property), the valuation date, the FMV conclusion, the valuation method used, and the specific basis for the valuation such as comparable sales or financial projections. The appraiser must also sign a declaration acknowledging that the appraisal will be used for tax purposes and that penalties apply for misstatements.¹⁴ Skipping any required element can disqualify the entire appraisal, which in turn disqualifies the deduction. A credential after an appraiser’s name isn’t enough; the report itself needs to check every box.

1
Internal Revenue Service. Publication 561 (12/2025), Determining the Value of Donated Property
2
eCFR. 26 CFR 20.2031-1 – Definition of Gross Estate; Valuation of Property
3
Office of the Law Revision Counsel. 26 US Code 2032 – Alternate Valuation
4
Office of the Law Revision Counsel. 26 US Code 1014 – Basis of Property Acquired From a Decedent
5
Office of the Law Revision Counsel. 26 US Code 1015 – Basis of Property Acquired by Gifts and Transfers in Trust
6
Office of the Law Revision Counsel. 26 US Code 170 – Charitable, Etc., Contributions and Gifts
7
Internal Revenue Service. Digital Assets
8
Internal Revenue Service. Frequently Asked Questions on Virtual Currency Transactions
9
National Constitution Center. The Fifth Amendment Takings Clause
10
Legal Information Institute. Just Compensation
11
Office of the Law Revision Counsel. 26 US Code 6662 – Imposition of Accuracy-Related Penalty on Underpayments
12
eCFR. 26 CFR 1.6662-2 – Accuracy-Related Penalty
13
Internal Revenue Service. Penalty Relief for Reasonable Cause
14
eCFR. 26 CFR 1.170A-17 – Qualified Appraisal and Qualified Appraiser