Layperson's Definition:

All processes used by a Party to verify that the inventory is of acceptable quality.

IPCC Definition:

Quality Assurance (QA) activities include a planned system of review procedures conducted by personnel not directly involved in the inventory compilation/development process to verify the data quality objectives were met, ensure that the inventory represents the best possible estimate of emissions and removals given the current state of scientific knowledge and data availability, and support the effectiveness of the quality control (QC) programme.