Paypal's Venmo app processed $2.1bn in payments in Q3 2015

"PayPal’s aim is not only to grow its customer base, but to create deeper, more relevant relationships with each of its customers. In the third quarter, the company processed 1.22 billion payment transactions, which translates to 27 payment transactions per active customer account. This is an increase from 24 payment transactions per active customer account in the same period last year. $2.1 billion of volume was processed through the Venmo product, growing over 200%, making it one of the fastest growing apps in the world by dollar volume."

Source:  BusinessWire, 28th October 2015

Note - Venmo is currently only available to US residents