Purpose This study examines whether supervisors' use of two relational (“soft”) influence tactics—collaboration and ingratiation—is associated with accountants' task performance via perceived leader–member exchange (LMX) quality, and whether perceived LMX quality conditions the relationship between job stress and task performance. Design/methodology/approach Integrating Leader–Member Exchange (LMX) and Conservation of Resources (COR) theories as dual-mechanism framework, proposing a dual-role model of perceived LMX quality as both a mediating mechanism and a buffering condition. Data were collected through a three-wave, time-lagged survey of 406 accountants working in Vietnamese small and medium-sized enterprises (SMEs) and analyzed using Partial Least Squares Structural Equation Modeling (PLS-SEM). Findings Collaboration and ingratiation were positively associated with perceived LMX quality. Perceived LMX quality was positively associated with task performance, and the indirect associations from both influence tactics to task performance via perceived LMX quality were statistically significant. In addition, job stress was negatively related to task performance; however, this negative association was weaker at higher levels of perceived LMX quality, indicating a buffering condition in the stress–performance relationship among accountants. Originality/value The study contributes to leadership and behavioral accounting research by identifying two relational antecedents of perceived LMX quality in accounting context and by modeling perceived LMX quality simultaneously as a pathway linking managerial influence tactics to performance and as a boundary condition that attenuates the negative job stress–task performance association.