Tax credit scholarship (TCS) programs offer state tax credits to individuals or businesses that donate to scholarship funds for students to attend private elementary and secondary schools. Through these credits, donors may reduce the amount they owe in state taxes by the full or a partial amount of their donation, depending on each program's rules. Designing a TCS program requires that many decisions be made, such as which students will be eligible to receive scholarships and the effect donations will have on donors' state taxes. The Government Accountability Office (GAO) was asked to review key characteristics of TCS programs. This report examines: (1) state TCS programs' policies regarding student eligibility and scholarship awards; and (2) how donating to a TCS program could affect the amount of state and federal taxes owed by donors. For both objectives, GAO reviewed publicly-available documents about student eligibility and tax provisions for all 22 programs authorized as of January 2018 and verified the accuracy of the information with state program officials. GAO also interviewed federal officials and reviewed relevant federal guidance and policy documents. Findings reveal that in 2018, there were 22 TCS programs authorized across 18 states, which provide state tax credits for individual and business donations that fund scholarships for students to attend elementary and secondary private schools. To determine the eligibility of students for these scholarships, most TCS programs use household income and have various approaches to determine scholarship award amounts. Income limits vary widely among programs, ranging from approximately $32,000 to $136,500 per year for students from a four-person household in school year 2017-2018. The effect of TCS donations on donors' tax liability depends on program characteristics and donors' financial circumstances. Specifically, half of the 22 programs allow eligible donors to claim 100 percent of their donations as state tax credits, meaning that for each dollar donated, state taxes owed are reduced by a dollar, up to any maximum set by the state. The remaining 11 programs allow donors to claim from 50 to 85 percent of their donations as state tax credits.