This paper presents a new nine-level switched-capacitor transformerless inverter topology featuring a common-ground configuration for photovoltaic (PV) and grid-connected applications. The proposed inverter achieves a quadruple voltage boost using a single DC source and employs twelve power switches, three self-balancing capacitors, and a single diode. The common-ground structure effectively eliminates leakage current by stabilising the common-mode voltage and ensuring enhanced safety. The design avoids the need for H-bridge or polarity reversal circuits, while maintaining balanced capacitor voltages without external sensors or controllers. A key feature is the reduction of switch voltage stress, with the maximum blocking voltage limited to the output voltage, unlike many recent topologies that require switches rated for 1.5 to 2 times the output voltage. Detailed operational analysis, component selection, and loss analysis have been presented. The topology’s performance is validated through MATLAB/Simulink and PLECS simulations, along with experimental testing on a 1.3 kW laboratory prototype. To highlight the merits of the proposed topology, a comprehensive comparison with the recent nine-level quadruple-boost inverter topologies is presented. © 2025 The Author(s).