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Federal Tax Research


This guide is identifies primary sources and explanatory secondary sources for federal tax law.  If you're new to tax law, you will probably want to first familiarize yourself with the primary and secondary sources listed below.  Use the navigation tabs at the top of the page to find more detailed information on each source.

Almost every source listed is available through one or more of the online tax research databases, which are linked in the Tax Databases box on the left.  As general legal research tools, Lexis Advance and WestlawNext provide access to these sources, but it is usually better to use one of the specialized tax research databases.  The call numbers of selected print sources are also provided.

U.S. Income Tax: The Constitution

The Congress shall have power to lay and collect taxes on incomes, from whatever source derived, without apportionment among the several States, and without regard to any census or enumeration.

U.S. Const. amend. XVI

Steps in Analyzing a Tax Problem

It's good practice to analyze a tax issue by reviewing the sources in the following order:

  1. Internal Revenue Code
  2. Treasury Regulations
  3. IRS Rulings and Decisions
  4. Case Law

You can begin your research process with secondary sources, but you should analyze a tax problem by following the basic steps outlined above.

Federal Tax Sources

Primary sources contain the law created by one of the branches of government:

Branch Type Source
 Legislative  Statutory

 Internal Revenue Code
 Other Federal Statutes
 International Tax Treaties
 U.S. Constitution

 Executive  Administrative/

 Treasury Regulations
 IRS Administrative Documents (Rulings, Procedures, etc.)

 Judicial  Case Law

 Federal Cases from:
     Supreme Court
     Circuit Courts of Appeals
     District Courts
     Court of Federal Claims
     United States Tax Court

Secondary sources are any source that explains, analyizes, or comments on a primary source:

Type Description
Handbooks, Deskbooks & Guides

Handbooks and guides provide short overviews of the tax law, often with simple annotations and cross references.  These are geared for practitioners, but can be a good starting point for someone starting out in tax research.

Tax Services

Tax services are comprehensive tools that are used to locate all the relevant primary authority related to a particular tax issue.  In print, these are found in multivolume, loose-leaf binders, but our primary access is online.


Citators can be used to track the history of a case, as well as to see which cases subsequently cited it.  There are specialized citators for tax law, and in addition to providing the history of a case and the cases that cited it, these also provide citations to all the relevant administrative rulings, decision and other documents by the IRS.


Treatises are comprehensive publications on specific areas of tax law, including detailed history of the law, analysis and commentary.  Like handbooks and guides, these can be a good starting point for research, but they go into much more depth than the handbooks and guides.

Journal Articles

Articles written by scholars and practitioners about specific issues in specific areas of tax law.


Tax Databases

For a detailed description see the Tax Research Databases tab.


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