The objective of this Mitigation Momentum Project paper is to identify open issues for the measurement, reporting and verification (MRV) of nationally appropriate mitigation actions (NAMAs) pertaining to key dimensions of MRV, as recognised by MRV literature and UNFCCC texts, namely: transparency, robustness and feasibility and cost-effectiveness. It pays particular attention to NAMAs with a supported component and reflects relevant experiences with developing NAMA proposals in the five Mitigation Momentum countries (Chile, Indonesia, Kenya, Peru and Tunisia). Key challenges analysed in this paper include: designing a MRV system that satisfies both host countries’ and funders’ expectations while complying with UNFCCC reporting requirements; drawing the line between the MRV approach for unilateral components and the MRV approach for supported components; and designing a pragmatic, implementable MRV system in line with a country’s capacities.