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A vegetable vendor waits for customers at a market in Kolkata, with a QR code displayed for digital payments

For most Indians, paying by Unified Payments Interface (UPI) has become almost absurdly routine.

Scan a QR code, tap a few buttons and the money moves instantly. There is no card machine, no cash, and - most importantly - for the user, no visible fee.

That may be about to change.

India has paved the way for banks and payment companies to charge merchants a fee on UPI transactions, potentially ending a decade-long experiment in free digital payments.

The government has yet to decide the rate or exactly where it will apply, but proposals under discussion include a merchant discount rate (MDR) of 0.3-0.5% - a small fee paid by a business to the banks and payment companies that process its UPI payments - on larger transactions at big businesses.

The government says consumers and person-to-person UPI payments will remain free.…