In some examples, methods and systems may process one or more payment transactions between a merchant and a customer by registering, by a biometric sensor of a payment object reader or a mobile device, a biometric characteristic as a biometric payment instrument, for example by obtaining data corresponding to a biometric characteristic of the customer. The data is converted into a digital signature of the biometric characteristic and compared with a registered biometric instrument at the time of transaction. If a match is obtained, the customer effects payments through the registered biometric instrument.