A contingent contract is an agreement to do or not do something depending on whether a future uncertain event that is collateral to the contract does or does not occur. For a contingent contract to be enforced, the uncertain future event must happen. The performance of a contingent contract depends on an act by the promisor if a specified event occurs within a fixed time period, but not on impossible events. Contingent contracts differ from wagering agreements in that they do not contain reciprocal promises and the future event is only collateral, not the sole determining factor.