A 403(b) plan is a U.S. tax-advantaged retirement savings plan available for public education organizations, some non-profit employers (only Internal Revenue Code 501(c)(3) organizations), cooperative hospital service organizations, and self-employed ministers in the United States. It has tax treatment similar to a 401(k) plan, especially after the Economic Growth and Tax Relief Reconciliation Act of 2001.
Employee salary deferrals into a 403(b) plan are made before income tax is paid and allowed to grow tax-deferred until the money is taxed as income when withdrawn from the plan.
403(b) plans are also referred to as a tax-sheltered annuity although since 1974 they no longer are restricted to an annuity form and participants can also invest in mutual funds.
Read more about 403(b): Regulation, Compliance, Bankruptcy Protection Before 2005, After-tax Contributions