The Microwave Radar-based Imaging Toolbox (MERIT) project aims to produce a robust, consistent framework for microwave imaging signal processing and reconstruction. Open-source scientific software has successfully been used in others domains, such as EIDORS for Electrical Impedance Tomography, MEEP for finite-difference time domain modelling, and gprMax for ground-penetrating radar. Open-source software in these domains has facilitated researchers to draw on collective expertise without having to re-implement commonly used algorithms. Similarly, MERIT contains reference implementations of leading microwave imaging algorithms and processing stages; enabling rapid development and testing of new microwave imaging software.