The U.S. Tax System Overview

The United States tax system is a complex framework of federal, state, and local taxes that funds government operations and services. Understanding the basics is essential for every taxpayer.

Constitutional Authority

The power to tax is established by the Sixteenth Amendment (ratified 1913), which authorizes Congress to levy an income tax without apportioning it among the states. The primary federal tax statute is the Internal Revenue Code (IRC), Title 26 of the United States Code.

Types of Federal Taxes

Individual income tax — the largest source of federal revenue; applied to wages, salaries, investment income, and other earnings

Corporate income tax — levied on the profits of C corporations

Payroll taxes — fund Social Security and Medicare (FICA taxes); split between employer and employee

Estate and gift taxes — imposed on transfers of wealth above certain thresholds

Excise taxes — levied on specific goods and activities (fuel, tobacco, alcohol, airline tickets)

Progressive Tax System

The U.S. uses a progressive income tax system with multiple tax brackets. As income increases, higher portions are taxed at higher rates. This is a marginal system — only income within each bracket is taxed at that bracket's rate, not all income.

The IRS

The Internal Revenue Service (IRS) is the federal agency responsible for:

Collecting federal taxes

Enforcing the tax code

Processing tax returns

Issuing regulations and guidance interpreting the IRC

Conducting audits and investigations

State and Local Taxes

In addition to federal taxes, most states impose:

State income tax — varies widely; seven states have no income tax

Sales tax — levied on retail purchases (rates and exemptions vary)

Property tax — typically levied by counties and municipalities on real property

State corporate taxes

Tax Policy Principles

Tax policy is evaluated using several criteria:

Equity — should taxes be based on ability to pay (progressive) or benefit received?

Efficiency — taxes should minimize economic distortion

Simplicity — the tax system should be understandable and administrable

Revenue adequacy — taxes must generate sufficient revenue for government operations

The U.S. Tax System Overview