G. Jyothi1 , R. Harish Kumar2, N. Surya Baskar3, K. Lokeswari4, A. Jaswanth5 03 3(1) The Unified Payments Interface UPI has transformed digital payment landscapes across India enabling instantaneous peertopeer transactions with over 10 billion monthly transactions by 2023 However centralized architectures inherent in current UPI systems present vulnerabilities including singlepoint failures data manipulation risks and inadequate fraud detection mechanisms This research proposes an innovative integration of blockchain technology with UPI infrastructure to establish a decentralized tamperresistant transaction validation framework The implemented system employs cryptographic hashing algorithms SHA256 digital signature mechanisms ECDSARSA and consensus protocols Proof of Authority to ensure transaction integrity authenticity and nonrepudiation A prototype developed using Python Web3js MongoDB and Ganache demonstrates enhanced security features including immutable ledger maintenance realtime fraud detection and comprehensive audit trails Experimental results indicate successful transaction validation with minimal latency overhead while providing superior security guarantees compared to conventional centralized systems The proposed architecture maintains UPIs characteristic transaction speed while introducing blockchains trust mechanisms thereby addressing critical security challenges in contemporary digital payment ecosystems Copyright (c) Journal of Science Engineering Technology and Management Science. All rights reserved 2026