The U.S. Government Accountability Office (GAO), Standards for Internal Control in the Federal Government (Green Book), sets the standards for an effective internal control system for federal and non-federal government agencies and provides the overall framework for designing, implementing, and operating an effective internal control system. The Green Book defines the standards through components and principles and explains why they are integral to an entity's internal control system. The Green Book clarifies what processes management considers part of internal control. In a mature and highly effective internal control system, internal control may be indistinguishable from day-to-day activities personnel perform. An entity uses the Green Book to help achieve its objectives related to operations, reporting, and compliance.
The Committee of Sponsoring Organizations of the Treadway Commission (COSO) updated its internal control guidance in 2013 with the issuance of a revised Internal Control - Integrated Framework. COSO introduced the concept of principles related to the five components of internal control. The Green Book adapts these principles for a government environment.