​Definition​ The fair market value (FMV) of any good or property refers to a price upon which the buyer and seller have agreed, when both parties are willing, knowledgeable, and not under direct pressure to carry out the exchange. The fair market value of a company’s stock refers to the price at which a company will issue stock to its employees, and is used by the IRS to calculate how much tax an employee owes on any equity compensation they receive. The FMV of a company’s stock is determined by the company’s most recent 409A valuation.