New Delhi, July 18 -- UPI's zero-fee model is back in focus as payment firms push for a limited merchant discount rate (MDR) on large transactions rather than across the board. Payment firms say costs are rising even as merchant acquisition slows and government incentives remain patchy, reviving the case for charging a small set of large merchants while keeping low-ticket payments free.

UPI processed 22.72 billion transactions worth Rs.28.92 trillion in June, averaging 757 million transactions per day. This scale has revived questions about who pays to keep the system running. Mint explains

MDR is the fee paid on a digital payment by the merchant's side to the bank and other payment players that move the money from the customer's accoun...