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Federal Tax Research Guide

A guide to conducting federal tax research.

About Treasury Regulations

Regulations are the highest administrative authority issued by the Treasury Department. They are published in the Federal Register and codified in Title 26 of the Code of Federal Regulations (CFR). Unlike other regulations, which are cited, for example, as "2 C.F.R. §342," Treasury Regulations are cited as "Treas. Reg. §1.123" without reference to the CFR.

Title 26 of the CFR is updated annually on April 1. Therefore, the researcher should utilize additional resources (such as CCH Standard Federal Tax Reporter or legal databases) to ensure that the most current version of the regulation is being consulted.

Treasury Regulations have a very organized numbering system. For example, Treas. Reg. § 20.7520-2(b)(3) indicates that this regulation is located in Title 26 of the Code of Regulations, part 20. It relates to Internal Revenue Code §7520. This cite is to subsection 2(b)(3) of the regulation.

The most commonly-seen parts of Title 26 of the Code of Federal Regulations are

  • 1 = Income Tax
  • 20 = Estate Tax
  • 25 = Gift Tax
  • 29 = Generation-Skipping Tax
  • 31 = Employment Tax
  • 301 = Procedure & Administration
  • 601 = Commissioner's Rules

Note: The number after the decimal point in § 601.xxxx Treasury Regulations does not refer to any particular section of the Internal Revenue Code.

A section of the Internal Revenue Code may have related Treasury Regulations in several different parts of Title 26 of the C.F.R. For example, Internal Revenue Code § 7520 (Valuation tables for annuities) has the following related regulations:

  • Treas. Reg. §1.7520-1 (regulation relating to the tables' use in income tax)
  • Treas. Reg. §20.7520-1 (regulation relating to the tables' use in estate tax)
  • Treas. Reg. §25.7520-1 (regulation relating to the tables' use in gift tax)

Often, a Treasury Regulation may have a subsection -0. This subsection is often a table of contents or an introduction to a series of related regulations.

A Treasury Regulation also has a "Treasury Decision" (T.D.) number. This number is chronologically-assigned. Both CCH and Thomson Reuters (formerly RIA)'s citators use the T.D. number rather than the Treasury Regulation cite as the point of entry into their print citators.

Types of Treasury Regulations

There are three types of regulations: (1) Proposed, (2) Temporary, and (3) Final.

Proposed Regulations (Prop.; Treas. Reg. §xxxx): Proposed regulations offer guidance to taxpayers seeking to comply with statutory rules, and provide the public an opportunity to submit comments on the proposed regulation. They may remain as proposed indefinitely. They are not published in the C.F.R., and are available only in the Federal Register, commercial finding aids and databases, and federal government websites.

Temporary Regulations (Treas. Reg. §xxxx-T): Temporary Regulations become effective when published in the Federal Register, are simultaneously published as Proposed Regulations in order to solicit public comments, and expire within 3 years unless made final. They are codified in the CFR and are located in numerical order mixed in with the final regulations. Temporary Regulations are not segregated out.

Final Regulations (Treas. Reg. §xxxx): The preamble to the regulation will state the effective date of the regulation. Note: the effective date is not the date the regulation is published in the Federal Register. Generally, the preamble is only available in the Federal Register, not in the codified regulation published in the CFR. However, annotated copies of the regulation, such as those in CCH Standard Federal Tax Reporter, Thomson Reuters Checkpoint, WESTLAW, or Lexis, will provide the researcher the Federal Register cite so that this information can be readily obtained.

Note: When using CCH, take note of the Regulation's Treasury Decision ("T.D.") number. You will use this number in CCH's citator to get the cite to the Cumulative Bulletin. The text of the regulation in the Cumulative Bulletin will have provide the cite to the Federal Register.

Weight Given

Courts give great weight to Legislative Regulations.  The related Internal Revenue Code section will state explicitly "The Secretary or his delegate shall prescribe such regulations as may be necessary."

Interpretive Regulations are all other regulations implemented under the Treasury Department's rule-making authority under IRC §7805. They are given "respectful consideration".

Proposed Regulations are given no more weight than an argument in a brief.

Special Bluebook Citing Rules


Please note that there are special Bluebook citation rules for tax-related administrative materials and court cases (see Bluebook (19th ed.) pp. 221 - 223.)


Commercial Databases


  • FTX-CFR = Final & Temporary Treasury Regs (CFR)
  • FTX-FR = Final, Temp., & Proposed Regs (Federal Register)


Go to taxation subject:

  • Treasury regulations—final, temp. & proposed
  • Treasury regulations—final & temp.
  • Treasury regulations—proposed

Federal Government Websites

Proposed, Temporary, and Final Regulations are available from the following government websites:

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