India’s Unified Payments Interface (UPI) had more than 55 crore users, the Centre said in July. The platform processed more than 80 crore transactions a day, according to National Payments Corporation of India (NPCI) data for October 2026.

A book chronicling the decades-long journey that culminated in the creation of UPI was launched in Calcutta on Saturday.

Cashless Nation, authored by Santanu Paul and B. Sambamurthy, is “captivating”, said Ashok Lahiri, vice-chairman of NITI Aayog and the chief guest at the launch programme at Bengal Club.

“Now UPI is approaching one billion transactions per day. Few tech inventions can claim to have scaled up so much,” Lahiri said.

“Scalability, shared technological infrastructure, freedom of choice and the principle of public good” were among the factors that made the system unique, he added.

Basudeb Banerjee, former chief secretary of Bengal; Saibal Chattopadhyay, chairman of the National Statistical Commission; and Praveena Rai, managing director and CEO of MCX, attended the launch.

Banerjee recalled November 8, 2016, when Prime Minister Narendra Modi announced demonetisation in a televised address.

Banerjee, who was then Bengal’s chief secretary, recalled rushing to meet chief minister Mamata Banerjee.

“She was livid. It took some effort to calm her down,” he recalled.

“The very next day, the chief minister decided to stage a protest at the RBI headquarters here,” he said.

The RBI chief in Calcutta at the time was new. Banerjee received a “panic call” from the local RBI chief. Eventually, the chief minister was “very nice” to her, Banerjee said.

The narrative non-fiction book traces the multi-decade journey of building a digital payments infrastructure on an unprecedented scale and examines how it transformed everyday relationships with money.

“UPI has put us at the top table of global payment systems. Many people think it is an exception. We are exporting this technology to several countries. We are giving it to their central banks. We are doing this as a goodwill gesture,” said Sambamurthy, a career banker who served as chairman of Corporation Bank and the NPCI.

Paul, a technocrat, entrepreneur and researcher, is a public interest director at the Bombay Stock Exchange and a former chairman of the NPCI Innovation Council.

“I come from an angle of innovation. He is a banker. He comes from an angle of compliance and regulation. This book needed a balance. Innovation and regulation are like an accelerator and brakes in a car,” Paul told Metro. “Half a billion people have UPI user accounts. The country has 10 crore merchants, of which 6.5 crore have UPI acceptance. Which means we are two-thirds of the way to 100 % of merchants and halfway to 100% of users,” he said.