The amount of carbon credits, determined by risk analysis or the rules of a particular standard, which are set aside and not commercialized to ensure validity of carbon credits from a project in the event of leakage or impermanence.
"Definitions and Jargon" Reducing Emissions from Deforestation and Degradation (REDD): A Casebook of On-the-Ground Experience. 2010. The Nature Conservancy, Conservation International and Wildlife Conservation Society. Arlington,Virginia.