The IRS definition relies on willing-buyer/willing-seller, both with reasonable knowledge of relevant facts. For inherited property, FMV at the date of death establishes the stepped-up basis.
Related terms
Step-Up in Basis
A federal tax rule (IRC §1014) that resets an inherited asset's cost basis to its fair market value on the date of the original owner's death.
Probate
The court-supervised process of validating a will, paying the deceased's debts, and transferring remaining assets to heirs.
Inheritance Tax
A state-level tax paid by the heir on the value of property received from a deceased person.