The Health Coverage Tax Credit (HCTC), which pays 65 percent of health Insurance premiums for 16,000 trade-displaced workers and others, is the only use of federal income tax credits to cover the otherwise uninsured. In pending legislation to reauthorize Trade Adjustment Assistance, Congress has an opportunity to address HCTC's major problems, including participation by only 15 percent of eligible workers and administrative costs that consume roughly a third of federal spending on the credit. HCTC teaches lessons about how to structure tax credits serving a larger group of uninsured, such as credits proposed by Republican and Democratic Presidential candidates.