Internal Revenue Service (IRS) — Tax forms, instructions, publications, regulations, tax statistics, taxpayer help, information for business, and electronic services.
Internal Revenue Service: Exempt Organization Search — Provides search engine for identifying tax exempt organizations.
Multistate Tax Commission — Organization of state governments working with taxpayers to administer tax laws that apply to multistate and multinational enterprises.
Social Security Administration — Provides comprehensive information regarding the Social Security Administration (SSA) and its programs and services.
U.S. Department of Justice - Tax Division — Provides information on the department's tax cases.
U.S. Department of the Treasury — Programs and services, current headlines, public information and treasury bureaus and offices.