IPCC Definition:

Verification refers to the collection of activities and procedures that can be followed during the planning and development, or after completion of an inventory that can help to establish its reliability for the intended applications of that inventory.

Typically, methods external to the inventory are used to check the truth of the inventory, including comparisons with estimates made by other bodies or with emission and uptake measurements determined from atmospheric concentrations or concentration gradients of these gases.

One verification exercise required in the IPCC Guidelines is that Parties should complete both the Reference and Sectoral Approaches for CO₂ emissions from fossil fuel combustion.  However, Parties are encouraged to implement other verification exercises on individual portions of their inventory.