This study examines the execution of investment plans among individual stock market investors in Kerala within a behavioural finance framework. While traditional finance assumes that rational investment planning naturally translates into optimal outcomes, behavioural evidence suggests that execution often deviates due to cognitive and emotional biases. Using primary data collected from 327 individual equity investors in Kerala, the study analyses the extent to which investors adhere to predefined investment plans and investigates variations in execution behaviour across socio-demographic characteristics. The findings reveal that the overall level of execution of investment plans is moderate, indicating persistent behavioural frictions despite awareness of rational planning principles. Significant differences in execution are observed across gender, educational qualification, occupation, income level, and investment experience, while age does not appear to be a differentiating factor. The results highlight that behavioural biases and contextual factors interfere with disciplined execution, thereby limiting rational investment outcomes. By explicitly focusing on the post-decision phase of investment behaviour, the study contributes to behavioural finance literature by demonstrating that execution constitutes a distinct and critical dimension of investor rationality. The findings carry important implications for investor education, advisory practices, and regulatory initiatives aimed at improving long-term investment outcomes...