A National Forest Monitoring System (NFMS) is a set of methods, activities and institutional arrangements that aim to produce high-quality, reliable data on activities in forests (Activity Data), including forest-carbon estimates (Emissions Factors), and is a key tool to assess whether the implementation of REDD+ activities, policies and strategies are resulting in measurable climate change mitigation. An NFMS is a component of the REDD+ MRV but itself also operates on measurement, reporting and verification (MRV) functions.

An NFMS must meet certain standards: (i) uses a combination of remote sensing and ground-based inventory approaches; (ii) provides estimates that are transparent, consistent and accurate, and that reduce uncertainties; and (iii) is transparent and available for review.