Discharge of contract
This means the fulfilment of the obligations imposed by a contract, or else an agreement to negate the contract or put one in its place. It can also mean a situation where a party may be released from his obligations by impossibility of performance or by operation of law. For example, alteration of a written instrument without the consent of the other party will preclude the party altering the instrument from taking action on it and release the other party from all obhgations.
Reference: The Penguin Business Dictionary, 3rd edt.