Consideration must be something promised for the present agreement. Therefore, an act taken or money paid in the past does not constitute consideration for the present agreement. Typically, the courts will not permit past consideration for a current transaction and will void an agreement if past consideration was utilized for the contract formation.
Existing duty is a promisee that already bound to perform an existing duty. Beyond the existing duty that which they are already contracted is consideration. In the orthodox view, performance of an existing duty does not constitute consideration for the new promise.
Performance of an existing duty is cannot constitute a consideration According to the law, performance of an existing duty is cannot constitute a consideration. Now seems that the performance of an existing duty may constitute consideration for a new promise, in the circumstances where no duress or fraud is found and where the practical benefits are to the promisor.