A necessary prerequisite for impactful climate mitigation action is the availability of suitable and reliable baselines of emissions. This is especially true for urban and city-level actions and strategies that need reliable local data about emissions to prioritize actions and investments to achieve the highest possible impact. We describe the work of the Carbon Track and Trace project (CTT) done in collaboration with the municipality of Trondheim, Norway, to better understand the current gaps in emission reporting and monitoring and discuss initial steps to address them.