Countries participating in a national level REDD+ approach would presumably need to report their reference level and emissions reductions/sequestrations to a body defined by the UN or defined in a bilateral agreement with a donor country (e.g., UNFCCC Secretariat).
Emissions reductions and increased sequestrations made through a REDD+ project or program need to be verified by an independent third party verifier. There are various companies that perform verification services. In the case of project activities, the verification process involves a review of the Project Design Document (PDD) and the methodologies used in the project. This includes an assessment of the project’s additionality, baseline, monitoring plan, and environmental and social impacts. Through the verification process, emissions reductions achieved by a project will be certified, at which point they can be sold, traded, or retired. It is still unclear whether independent verification would be required for national-level REDD+ programs.