Millions of individual and business taxpayers owe billions of dollars in unpaid federal tax debts, and the IRS expends substantial resources trying to collect these debts. Other federal agencies that are owed non-tax debts report such debts to credit bureaus, in part as a tool to encourage debtors to pay. However, the IRS is not allowed to directly report tax debts to credit bureaus because long-standing federal law protects the privacy of taxpayers' information. This book examines the inventory of tax debts and the characteristics that may be relevant to a potential proposal to report tax debts to credit bureaus.