The reassuring part of the new Unified Payments Interface (UPI) framework is that customers will apparently not be charged for using UPI. The more interesting part is who, then, pays for keeping one of the world’s most widely used digital-payment systems running. From October 15, a Merchant Discount Rate (MDR) of 0.4 percent will apply to specified person-to-merchant transactions above Rs. 2,000, with a ceiling of Rs. 300 on transactions of Rs. 75,000 or more. Person-to-perso