Since its formation in 1997 Sound Transit has to become an agency that is known for effectively delivering projects and service around the region and maintaining accountability to the people it serves. Sound Transit is one of the most closely reviewed and audited agencies in the state. The state’s 2007 performance audit of Sound Transit identified 48 different federal, state and independent audits going back to before voters approved the Sound Move ballot measure in 1996.

Since 1997, Sound Transit has contracted with a national accounting firm to conduct annual financial audits. The Washington State Auditor's Office also performs a yearly review of the agency. Most recently, the Washington State’s Auditor’s Office issued an accountability audit of Sound Transit in 2007 that gives the agency a clean bill of health on its compliance with a broad array of state laws and regulations regarding handling of public dollars and maintaining public transparency.

Sound Transit’s system expansion options are independently reviewed by an Expert Review Panel appointed by the Governor and Legislature. The panel reviews the methodologies that the agency uses for estimating the costs of adding projects and service and projecting future ridership for the options under review.