There is an urgent need to decarbonise transport systems across all modes, including light commercial vehicle (LCV) fleets. This paper introduces eFleetPlan, an open-source software designed to support decision-making on LCV fleet electrification by jointly optimising investments in charging infrastructure and fleet charging operations. Developed in Python, eFleetPlan is a modular, transparent tool that enables data-driven planning for electric LCV fleets. This tool includes two packages: fleet operation simulation and the charging co-optimisation. The co-optimisation package incorporates a mixed-integer linear programming (MILP) model that minimises infrastructure and operational costs while meeting fleet demand and energy constraints. Its flexible architecture allows adaptation to different geographical contexts, datasets, and operational assumptions, supporting applications in research, education, and practical fleet planning.