This deliverable presents the modelling of cell-to-module (CTM) losses in perovskite/Si tandem solar modules, with a focus on tandem-specific effects not observed in conventional silicon technologies. The work combines advanced optical and electrical models to analyse how module design influences current mismatch between the sub-cells and its impact on performance. Results show that while most CTM loss mechanisms are similar to silicon modules, current mismatch plays a critical role, affecting both efficiency and stability. The findings provide guidance for optimising module layout, demonstrating that appropriate design can reduce CTM losses and improve long-term module performance without requiring changes to standard string and bypass diode configurations.