UPI and India's Digital Payments Revolution

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Walk into a vegetable market in Pune or hail an autorickshaw in Coimbatore and you will find a laminated square of black and white pattern taped to a pole or hung from a handlebar. The customer points a phone at it, types an amount and a four or six digit code, and the money moves from one bank account to another in about two seconds, at no cost to either party. That is the Unified Payments Interface, usually called UPI, and it has done something no comparable system anywhere has quite managed: it has made instant bank to bank payment the default for very small transactions, including transactions of ten or twenty rupees that no card network would find worth processing.

UPI is run by the National Payments Corporation of India, an organisation whose structure explains a great deal about why the system works the way it does. NPCI was established in 2008 as a not for profit company under the guidance of the Reserve Bank of India and the Indian Banks Association, jointly owned by banks rather than by a listed corporation. It is therefore not obliged to maximise revenue from the payment rails it operates. UPI was launched in pilot form in April 2016 and opened to the public later that year, built on top of an earlier real time transfer service called IMPS that NPCI had introduced in 2010.

How it actually works

The design solved three problems at once. The first was addressing. Instead of exchanging account numbers and bank branch codes, a UPI user has a virtual payment address, a short identifier resembling an email address, or simply a mobile number. The payer never learns the recipient's account details. The second was interoperability. UPI is a common protocol rather than a product, so any bank and any authorised app can plug into it and every user can pay every other user regardless of which bank or app either side uses. This is the crucial difference from closed wallet systems, which fragment users into networks that cannot reach each other. The third was authentication. A payment is authorised by a PIN entered on a phone that has been cryptographically bound to the user's mobile number and bank account, which gives two factors without requiring a card, a reader or a one time password sent by text.

Two events accelerated adoption enormously. In November 2016 the Indian government withdrew the five hundred and one thousand rupee notes from circulation overnight, removing the large majority of currency by value and forcing tens of millions of people to look for alternatives during the weeks of shortage that followed. The government launched a basic reference app called BHIM in December 2016 into that gap. Then, from January 2020, the merchant discount rate on UPI payments was set to zero by law, meaning a shopkeeper pays nothing to accept a UPI payment. Card acceptance in India had always been limited by the fee a small trader had to absorb. Removing the fee removed the reason not to accept.

The result is a volume figure with no precedent. UPI passed ten billion transactions in a single month during 2023 and has continued climbing since, and it now accounts for the large majority of retail digital payment transactions in India by count. The user facing market is dominated by a small number of third party apps, principally PhonePe, Google Pay and Paytm. NPCI announced in 2020 that no single app would be permitted more than thirty per cent of transaction volume, but the deadline for enforcing that cap has been deferred repeatedly, because enforcing it would mean turning away real customers from apps they already use.

The pieces around the edges

UPI sits inside a broader set of public digital infrastructure that Indian officials call India Stack. Aadhaar, the biometric identity number, supplies remote verification. The Jan Dhan financial inclusion programme, launched in 2014, opened bank accounts in enormous numbers so that there was something for a payment system to connect to. Extensions have followed: UPI 123PAY, introduced in 2022, allows payments from a basic feature phone through an interactive voice menu, addressing users with no smartphone at all; UPI Lite handles very small payments on device to reduce load on bank servers; AutoPay handles recurring mandates; and RuPay credit cards can now be linked to UPI, which quietly reintroduces a fee bearing product into a fee free system.

The model has been exported. NPCI's international arm has linked UPI to Singapore's PayNow for cross border transfers, and acceptance arrangements now exist in the United Arab Emirates, Nepal, Bhutan, Sri Lanka, Mauritius and France, generally aimed first at Indian travellers and at remittance corridors. India used its presidency of the Group of Twenty in 2023 to promote the broader idea of digital public infrastructure as an export, and several countries have signed agreements to adapt elements of the Indian stack.

The unresolved problems

The absence of a fee is the system's greatest strength and its central vulnerability. Someone has to pay for the servers, the fraud monitoring and the settlement, and at present that cost falls on banks and app operators with partial compensation from a government incentive scheme announced each year. Whether a payments network of this scale can be sustained indefinitely without a price is a genuinely open question, and bank associations have argued publicly for a small merchant fee on large businesses while the government has repeatedly ruled it out.

Fraud has grown alongside volume. The typical scam is social rather than technical: a caller persuades the victim to approve a collect request, or to enter a PIN on the pretext of receiving money rather than sending it, and the speed and irreversibility that make UPI convenient also make recovery difficult. The Reserve Bank and NPCI have added friction for first time payees and limits on new accounts.

There are also structural concerns. Two of the three dominant apps are owned by companies headquartered outside India, which regulators view as a concentration risk in critical infrastructure. Outages at a single major bank can degrade the experience for millions. And the inclusion story is incomplete: participation requires a bank account, a phone and a level of literacy that not everyone has, and cash in circulation in India has continued to grow in absolute terms even as digital payments have exploded. UPI has clearly changed how urban and increasingly rural India transacts. Whether it has displaced cash, or simply added a very large new layer on top of it, is still being argued over with reasonable evidence on both sides.

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