The United States has separate federal, state, and local governments with taxes imposed at each of these levels. Taxes are levied on income, payroll, property, sales, capital gains, dividends, imports, estates and gifts, as well as various fees. In 2020, taxes collected by federal, state, and local governments amounted to 25.5% of GDP, below the OECD average of 33.5% of GDP.

The United States federal government and most state governments impose an income tax. They are determined by applying a tax rate, which may increase as income increases, to taxable income, which is the total income less allowable deductions. Income is broadly defined. Individuals and corporations are directly taxable, and estates and trusts may be taxable on undistributed income. Partnerships are not taxed, but their partners are taxed on their shares of partnership income. Residents and citizens are taxed on worldwide income, while nonresidents are taxed only on income within the jurisdiction. Several types of credits reduce tax, and some types of credits may exceed tax before credits. Most business expenses are deductible. Individuals may deduct certain personal expenses, including home mortgage interest, state taxes, contributions to charity, and some other items. Some deductions are subject to limits, and an Alternative Minimum Tax (AMT) applies at the federal and some state levels.