India built the world's biggest digital payments miracle. Now comes the bill

India's Unified Payments Interface (UPI) has transformed the country's digital payments landscape, becoming an almost automatic part of daily life for most Indians. By scanning a QR code and tapping a few buttons, users can transfer money instantly, with no visible transaction fees. This innovation has paved the way for banks and payment companies to charge merchants a small fee, known as the Merchant Discount Rate (MDR), on larger UPI transactions, potentially ending a decade of free digital payments.

The government is currently debating the rate and scope of these merchant fees, with proposals suggesting a MDR of 0.3-0.5% for larger transactions at major businesses. However, the government has emphasized that consumer and person-to-person UPI payments will remain fee-free. Introducing merchant fees could potentially weaken the network that has contributed to UPI's success.

Launched in 2016, UPI has grown to process an astounding 23.6 billion transactions worth 29.87 trillion rupees ($313.5bn; £232.2bn) in a single month. Fintech apps like PhonePe and Google Pay dominate UPI payments, with over 550 million users and the system now available in 11 countries outside India. UPI's design is unique, as it creates a common digital infrastructure that allows competing companies to operate on the same platform.

This merchant network has been instrumental in driving UPI's adoption, as even small businesses like vegetable sellers, taxi drivers, and shopkeepers can accept payments through a printed QR code without the need for a card terminal. Economists believe that merchant acceptance has been a key driver of UPI's growth. If a fee is imposed on small and informal merchants, especially in districts with still-developing acceptance networks, it could potentially slow the merchant expansion that has been crucial to UPI's scaling.

However, the government aims to minimize this risk by proposing to target fees at transactions above 2,000 rupees at larger merchants, leaving small businesses and low-value payments effectively untouched. This approach could generate a significant new revenue stream for banks and payment companies while preserving the everyday affordability of UPI payments.

The challenge lies in balancing UPI's financial sustainability with the conditions that contributed to its widespread adoption.