Preexisting Duty Rule
preexisting duty rule n: a common-law rule of contracts: a party's offer of a performance already required under an existing contract is insufficient consideration for modification of the contract NOTE: This rule is not applicable to sales contracts in jurisdictions that have enacted the Uniform Commercial Code. It is also not applicable where there has been a rescission of the contract followed by a new contract.
Source: Merriam-Webster's Dictionary of Law ©1996. Merriam-Webster, Incorporated. Published under license with Merriam-Webster, Incorporated.