The Retailers Association of India has warned that the new UPI merchant fee could encourage some small retailers to return to cash transactions.
UPI merchant payments above Rs 2,000 will attract a new charge from October 15, but consumers will continue to use UPI free of cost.
PM Modi has called for wider global adoption of UPI, highlighting India's digital payments success and fintech growth at Fintech Fest.
The Finance Ministry has dismissed speculation about imposing a Merchant Discount Rate on UPI transactions, calling such claims false and misleading.
Apple Pay services including Wallet, Card, and Cash were down globally for over two hours on May 16, causing widespread payment failures.