The Patient Protection and Affordable Care Act (ACA; P.L. 111-148, as amended) included a provision to impose an excise tax on high-cost employer-sponsored insurance (ESI) coverage beginning in 2018. This provision, popularly termed the Cadillac tax, imposes an excise tax on ESI coverage in excess of a predetermined threshold. The tax is imposed on the coverage provider, typically the health insurance provider or the entity that administers the plan benefits. Currently, employers' spending on ESI coverage and most employees' contributions to ESI plans are exempt from income and payroll taxes. Although proposals to limit the amount of health insurance benefits eligible for this exclusion were considered, the ACA, as enacted, did not limit the exclusion for employer-provided health insurance coverage. The Cadillac tax discourages high-cost employer health plans through another approach. This book examines several issues. It evaluates the potential of the Cadillac tax to affect health insurance coverage and the health care market. It also examines the expected incidence (burden) of the tax -- that is, which group's income will be reduced by the tax. Finally, the book discusses implications for economic efficiency in the context of tax administration.