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Federal Tax Law Research: Primary Law

A starter's research guide to the resources and tools available when researching federal tax law, with emphasis on primary law sources, administrative law materials, major tax law databases, and major secondary tax law sources.

Types of Primary Law

U.S. Code

At the Federal level, tax statutes are codified in Title 26 of the U.S. Code (also known as the Internal Revenue Code). Title 26 is available in many places both in print in the Law Library and online.



There are two commercially published, annotated versions of the U.S. Code. These versions are unofficial, but contain annotations or editorial enhancements which provide interpretative information, cross-references, citations to related content and law, and legislative history materials.


A number of resources containing Title 26, either free or by paid subscription, are also available online. Please note that most subscription based resources (Westlaw, Lexis and Bloomberg) will contain annotations, while no-cost resources listed will contain only the text of the law itself.

Case Law

An essential part of interpreting the meaning and practical application of statutory tax law is determined through case law. Federal tax disputes are heard before the U.S. Tax Court, the U.S. District Courts, and the U.S. Court of Federal Claims. Appeals are heard through the U.S. Courts of Appeals. Circuit court decisions are appealed to the U.S. Supreme Court. Tax case decisions are available through all of the major tax databases (RIA, CCH/Cheetah, Bloomberg Law), through government websites (such as court sites), and through print reporters in the Law Library.

Hierarchy of Tax Courts

Web Resources

Print Resources

Tax Court Decisions (1924-2016)

District Court Decisions

Court of Federal Claims & Court of Appeals Decisions

U.S. Supreme Court Opinions

Source of Regulations

Regulations are rules promulgated by executive agencies, such as the IRS. Treasury Regulations (Treas Regs) promulgated by the IRS are considered primary authority and have the full force of law. These regulations are the official interpretation of the Internal Revenue Code.

Regulations are published as soon as they are promulgated and can be found within the Federal Register: the official published version of executive agency proposed and final rules.

The Fed Reg, current and past issues, can be found online.

  • Federal Register

*Please note that while the Federal Register is published in print, the Law Library no longer subscribes to the print version.

Final rules and regulations are published in the Code of Federal Regulations or CFR.  The CFR is published annually and updated on a staggered basis, four times per year. It is arranged by topic area, then by agency/office. Access to the CFR is available both online and in print at the Law Library.

  • Code of Federal Regulations



Temporary Regulations

Temporary Regulations are also often promulgated by the IRS. These regulations are effective upon publication and last 3 years. Some temporary regulations issued before the statutorily-defined 3 year period requirement (pre-1988) may still be in effect. These regulations do not go through the traditional notice and comment rulemaking that other Treas. Regs. undergo but are treated as having the same authority as final regulations.

*Temporary regulations can also be found on most commercial databases with the Fed Reg and IRBs (e.g. Westlaw, Lexis, Bloomberg, CCH, and RIA Checkpoint).

IRS Bulletins

The IRS also issues a bulletin, known as IRB, which is an official newsletter-type publication of the IRS. The IRB publishes recently promulgated Treas Regs, then known as Treasury Decisions (TDs). An archive of past issues and an updated list of current issues is available on the website. More information about the IRB can be found under the Additional Resources tab of this guide.


Note About Treasury Regulations Citations

Although Treasury Regulations are codifed in Title 26 of the Code of Federal Regulations, Treas Regs are not cited as CFR sections, but rather, as their own type.

e.g. 26 CFR 1.1401-1 (2013) would be cited as Treas. Reg. §1.1401-1 (2013).