Pre-existing Duty Rule

In one sentence

A principle that performing an obligation you already owe is not valid consideration for a new promise.

Plain English

The pre-existing duty rule says you can't use something you're already legally required to do as the basis for a new contract. For instance, if a police officer promises to investigate your case in exchange for money, that's not a valid deal because investigating is already their job. You need to offer something new or different to create enforceable consideration. Modern contract law has softened this rule in some situations, especially when both parties agree to modify a contract and there's a legitimate reason for the change.

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Example

A contractor agrees to build your house for $200,000. Midway through, he says he won't finish unless you pay an extra $50,000. You refuse because he's already obligated to complete the job; his promise to finish isn't new consideration for the extra payment.

Used in a sentence

“The court rejected the modification because the employee's continued work was subject to the pre-existing duty rule and could not serve as consideration.”

Related terms

Bargained-for Exchange

A mutual agreement where each party gives something of value in return for something from the other.

Voidable Contract

A contract that one party can cancel or reject, but is otherwise valid.

Mutual Mistake

Both parties are wrong about a basic fact when they sign a contract.

Conditions Precedent

An event that must happen before a party's obligation under a contract kicks in.

Offer

A proposal to enter into a binding agreement on specific terms.

Acceptance

Agreeing to the exact terms of an offer, creating a binding contract.

Consideration

Something of value exchanged by each party to make a contract binding.

Offeror

The person who makes an offer to enter into a contract.

This page is a plain-English reference and is not legal advice. Laws vary by jurisdiction and change over time. For specific situations consult a licensed attorney.