Which principle allows a party to enforce a promise to pay even without new consideration when the promise was relied upon to the promisee’s detriment?

• A. Parol evidence rule
• B. Promissory estoppel
• C. Statute of limitations
• D. Mailbox rule

Answer: (B)

Promissory estoppel is the principle that allows enforcing a promise without new consideration when the promise is relied on to the promisee’s detriment to prevent injustice. When someone makes a clear, definite promise and the other person reasonably relies on it, acting or forbear­ing in reliance (such as spending money or giving up a benefit), the law can enforce the promise even though there isn’t a new bargain supported by consideration. The key elements are a definite promise, reasonable reliance by the promisee, actual detriment from that reliance, and the need to prevent injustice. The parol evidence rule, statute of limitations, and the mailbox rule address different legal issues—interpretation of written contracts, timing of when a lawsuit must be filed, and when an acceptance becomes effective, respectively—so they don’t govern enforcement based on reliance without consideration.