Which term describes a contract that is valid but may be rejected by one party later?

The term that describes a contract that is valid but may be rejected by one party later is "voidable." A voidable contract is one that is legally binding and enforceable on its face, but it includes conditions that allow one or more parties to void or cancel the contract under certain circumstances. This can occur due to factors like misrepresentation, duress, undue influence, or the incapacity of one of the parties at the time the contract was formed.

In a voidable contract, the affected party has the right to affirm or reject the contract, meaning they can choose to uphold the contract or let it lapse without facing legal consequences. The distinction here lies in the validity of the contract; it is still considered valid until the affected party decides to void it.

Other terms such as "unenforceable" refer to contracts that cannot be enforced due to certain legal defenses or issues, "null" implies that the contract was never valid from the start, and "completed" indicates that all obligations under the contract have been fulfilled. Thus, none of those terms capture the essence of a contract that remains valid but provides an option for one party to withdraw their commitment.