Financial accounting recognizes gains based on commercial substance while tax accounting defers gains and losses for like-kind exchanges. For tax purposes, the realized gain or loss equals the fair market value of everything received minus the tax basis of everything surrendered, and the recognized gain can never exceed the realized gain. Boot refers to non-like-kind property, such as cash, received in an otherwise like-kind exchange, and the receipt of boot can trigger gain recognition up to the value of the boot received.