Digital Disruption, Consumer Behaviour, UPI, Tier-2 Consumption, Financial Inclusion, Impulse Purchasing. This study investigates the structural shift in consumer spending behaviour within Tier-2 cities in India and globally from 2020 to 2026, driven by real-time digital payment systems like the Unified Payments Interface (UPI) and mobile wallets. Historically, non-metro consumption was constrained by physical cash cycles, limited banking access, and high transactional friction. Leveraging a mixed-methods framework, this paper analyses secondary macroeconomic indicators alongside primary empirical survey data (N = 350) collected from Tier-2 urban ecosystems. Employing descriptive analytics, Chi-Square Independence Tests, and correlation modelling, the research evaluates how the mitigation of the "pain of paying" alters transaction frequency, discretionary ticket sizes, and impulse purchasing. The findings show a statistically significant transition from cash-dependent essential purchasing to digital-first discretionary spending, with over 60% of new e-commerce and retail growth originating from non-metro areas. The study demonstrates that digital payment infrastructure acts as a primary catalyst for financial inclusion and consumption smoothing, carrying profound implications for retail strategy, regional market penetration, and fiscal policymaking.