UPI, launched in 2016 by NPCI under RBI's oversight, processed over 172 billion transactions worth ₹246 lakh crore in FY 2024-25, averaging roughly 1 billion transactions daily. The system operates on an interoperable, 24×7 instant payment rails architecture linking over 650 banks. It now powers merchant payments, person-to-person transfers, credit-on-UPI, and cross-border remittances. UPI's global footprint extends to 8 countries including Singapore, UAE, France, and Bhutan through bilateral payment linkage agreements.

UPI (Unified Payments Interface) is a real-time payment system developed by the National Payments Corporation of India (NPCI) and regulated by the Reserve Bank of India. It operates on a two-tier architecture: the payment layer (UPI app) sits on top of the settlement layer (IMPS — Immediate Payment Service), which provides 24×7 interbank fund transfer.

What makes UPI structurally distinct from older systems is its Virtual Payment Address (VPA) model. Instead of sharing bank account details, users transact via a VPA (e.g., name@bankname), abstracting sensitive data. The system supports multiple payment flows: P2P (peer-to-peer), P2M (peer-to-merchant), and now P2PM (small merchants).

For exam purposes, key structural facts matter: NPCI is a 'not-for-profit' company promoted by a consortium of banks including RBI and IBA. UPI settlement happens in real time via IMPS rails. The system is governed under the Payment and Settlement Systems Act, 2007.

Recent regulatory additions include UPI Lite (for small-value offline transactions up to ₹500 per transaction, wallet limit ₹2,000), Credit Line on UPI (pre-sanctioned credit lines linked to UPI ID), and UPI One World (for foreign nationals visiting India). The RBI has also enabled UPI for feature phones via UPI123Pay.

International expansion is policy-significant: linking with Singapore's PayNow, UAE's AANI, and others reflects India's push for bilateral real-time payment interoperability — a SEBI and RBI-adjacent exam topic.