Pre-existing duty CASES

In English contract law, a pre-existing duty refers to obligations a party is already legally bound to perform, which generally cannot serve as valid consideration for a new promise.

Definition and Principles

Under traditional rules, performing or promising to perform an existing duty – either contractual or statutory – doesn’t usually constitute valid consideration unless the obligation significantly changes or provides additional benefit.

Common Examples

• Promises to pay more for the same contractual performance (often unenforceable).
• Public servants promising performance of duties already legally owed.
• Contracts where duties are expanded or significantly modified.

Legal Implications

• Promises based solely on pre-existing duties typically unenforceable.
• Additional consideration or practical benefit required to validate new promises.

Practical Importance

Understanding pre-existing duties prevents ineffective agreements, clarifies obligations, and guides parties in negotiating enforceable contract modifications.