Legal Definitions - preexisting duty

A preexisting duty refers to an obligation that a person is already legally bound to perform, either by law or by a prior contract. When someone promises to do something they are already obligated to do, this promise generally cannot serve as valid "consideration" for a new contract. In contract law, "consideration" means each party must give up something of value or incur some detriment for the contract to be enforceable. If a party is merely promising to fulfill an existing duty, they are not providing anything new of value to support a new agreement.

Here are some examples to illustrate this concept:

• Contract Modification: Imagine a construction company is hired to build a new office building for a fixed price of $10 million. Halfway through the project, they inform the client that they will stop work unless the client agrees to pay an additional $1 million due to unexpected material costs. The client, desperate to avoid delays, agrees to the extra payment.

  Explanation: The construction company already had a contractual duty to complete the building for the original $10 million. Their promise to finish the building, which they were already obligated to do, does not provide new "consideration" for the client's promise of an additional $1 million. Therefore, the agreement for the extra payment might not be legally enforceable because the construction company was merely promising to perform a preexisting duty.

• Public Official's Duty: A local police officer is investigating a series of burglaries in their assigned precinct. A concerned citizen, whose home was recently targeted, offers the officer a substantial cash reward if they successfully apprehend the culprit.

  Explanation: The police officer, as part of their employment and public service, already has a legal duty to investigate crimes and apprehend suspects within their jurisdiction. Their promise to investigate and catch the burglar is a performance of a preexisting duty. Therefore, the citizen's offer of a reward, if framed as a new contract for the officer to do their job, would likely not be enforceable because the officer is not providing new consideration beyond their existing obligations.

• Employment Agreement: An employee is under a written contract to work 40 hours per week for a specific salary. Their manager approaches them and says, "If you promise to work your regular 40 hours next week, I'll give you a $500 bonus."

  Explanation: The employee already has a contractual duty to work 40 hours per week for their salary. Their promise to work those same 40 hours next week is merely a promise to fulfill a preexisting duty. As such, this promise alone would not typically constitute new consideration to make the manager's offer of a $500 bonus a legally binding new contract, unless the employee agreed to perform *additional* duties or work *beyond* their existing contractual obligations.