1. A computer implemented method for providing promotional rewards, the method comprising: displaying in a networked device of a buyer at least one promotional offer for a product or service of at least one seller; allowing the buyer to accept electronically the promotional offer; allowing the buyer to submit a digital image of at least one receipt obtained from the seller whose promotional offer was accepted by the buyer; checking compliance of purchase data on the submitted receipt with the conditions of the promotional offer; and electronically computing a reward to be given to the buyer according to at least the conditions of the promotional offer.