Reports by the public of suspected underreporting of taxes or other tax violations can help IRS detect millions of dollars in taxes that would otherwise go uncollected. Productive referrals can help address the net $385 billion tax gap--the difference between the amount of taxes paid voluntarily on time and the amount owed. IRS received about 87,000 information referrals in fiscal year 2015. This book describes IRS’s process for screening and routing information referrals; assesses the controls for the information referral screening and routing process; and evaluates the coordination between the information referral process, the Whistleblower Office, and other IRS referral programs.