Each year, the U.S. Environmental Protection Agency (EPA), in cooperation with other federal agencies, prepares an Inventory of U.S. Greenhouse Gas Emissions and Sinks (here referred to as the Inventory). The emission estimates, trends, and other results of the inventory are used for a variety of purposes, including monitoring and tracking the progress of the United States in meeting commitments under the United Nations Framework Convention on Climate Change (UNFCCC). The United States has developed a comprehensive approach to preparing the inventory and the associated official documentation and communications that accompany and report the estimates. One of the primary goals of the U.S. Greenhouse Gas Inventory Program is to work continually to improve emission estimates. To this end, the U.S. inventory program has adopted a comprehensive and unified approach to managing quality and uncertainty in the inventory estimates. The philosophy underlying the approach is that methodological advances, improvements in documentation and clarity to facilitate transparency, quality control and quality assurance, and uncertainty analysis should all be integrated into one comprehensive greenhouse gas inventory system. This document is one of two complementary documents that together describe and provide guidance on the overall process of preparing, submitting, and disseminating a greenhouse gas inventory that has undergone quality control (QC) and quality assurance (QA) procedures.