This chapter discusses the law on discharge by agreement. An agreement by the parties to an existing contract to extinguish the rights and obligations which have been created is itself a binding contract, provided that it is either made under seal or supported by consideration. Consideration raises no difficulty if the contract to be extinguished is still executory, for in such a case each party agrees to release his rights under the contract in consideration of a similar release by the other. The discharge in such a case is bilateral, for each party surrenders something of value. Unilateral discharge occurs when the contract to be extinguished is wholly executed only on one side – as for instance where a seller has delivered the goods but the buyer has not paid the price. A unilateral discharge is usually ineffective unless it is made under seal or unless some valuable consideration is given by the buyer. Difficult problems arise where the agreement is designed to vary the contract.