Introduction There are several payment markets that can be identified, each using specific forms of money. The business-to-consumer (B2C) payment is used in commercial activities where the merchant is paid directly by the consumer for goods or services. This type of payment is also called retail payment. The direct payment between persons is called person-to-person (P2P) or even consumer-to-consumer (C2C). Administration-toconsumer (A2C) payment addresses the payment of taxes toward the government. Finally, the payment interveni ng between companies buying and those offering products and services is referred to as business-to-business (B2B) payment. A payment instrument refers to a form of money. A payment mechanism or payment method refers to the way a payment instrument is used to complete a payment transaction. Certainly, the range of payment instruments and payment mechanisms for B2C payments is different from the set of instruments available for other types of payments. This book analyzes only electronic payment instruments for B2C payments. ng between companies buying and those offering products and services is referred to as business-to-business (B2B) payment. A payment instrument refers to a form of money. A payment mechanism or payment method refers to the way a payment instrument is used to complete a payment transaction. Certainly, the range of payment instruments and payment mechanisms for B2C payments is different from the set of instruments available for other types of payments. This book analyzes only electronic payment instruments for B2C payments.