"Unified Payments Interface" (UPI), an innovative mobile-based payment system, was introduced by the Government of India to support its digitization initiatives. Not just in India, UPI has expanded globally by being implemented in Bhutan and is on the verge of being launched in ten more countries in north and southeast Asia and, the UAE & Africa. Thus the study examines UPI's growth and significance to the transformation of India's mobile payment systems, its global reach and further expansion. The study consists of two parts, with an initial focus on scholarly literature published in the last five years since the UPI's inception in April 2016. Out of 177 papers, the method yielded 14 notable peer-reviewed publications. Other sources include government policy papers, news materials, and research undertaken by national or international organizations such as Kantar, Statista, ASSOCHAM, Deloitte, Nielson, Ericsson, etc. Despite its early launch, UPI swiftly outperformed all other digital payment methods in India, including mobile wallets. Google Pay, PhonePe and Paytm were early drivers of UPI payments. However, the government-backed Bharat Interface for Money application failed to achieve its potential. Moreover, the Covid-19 pandemic has little impacted the growth of UPI. Another major finding is that transaction failure, and cyber frauds must be addressed for improved UPI uptake, and a greater focus will be on credit and cash withdrawals via UPI. The study concluded that Near field communication-based UPI payments will revolutionize peer-to-merchant payments.