Section 7805 of the Internal Revenue Code (IRC) enables the Treasury Department to interpret and administer the IRC. The Treasury Department by way of the Internal Revenue Service promulgates regulations and other guidance that administers and interprets the IRC. 

Tax regulations are consolidated into Title 26 of the Code of Federal Regulations (CFR). The sections of this title relate to the sections of Title 26 of the United States Code, which is the Internal Revenue Code (IRC), by the use of corresponding section numbers. Thus, in a typical CFR section number, the corresponding IRC section number follows the decimal point. For example, CFR section 1.102-1 interprets or implements IRC section 102. The number preceding the decimal point correlates to general subject areas in the IRC. For example, regulations dealing with income tax have a “1” preceding the decimal point.

When initially published by the Internal Revenue Service, new final regulations are called Treasury Decisions (TDs). Final and proposed regulations are issued as Treasury Decisions before they are codified in the Code of Federal Regulations.  The Treasury Decisions contain explanatory preambles which are not included in the C.F.R. When eventually codified in Title 26 of the CFR, they are referred to by CFR citation. However, some tax services continue to use TD numbers as cites, rather than CFR section numbers.

Proposed Regulations​​

Proposed regulations are regulations that have been proposed by the Department of Treasury but are not yet formally adopted.  They are published in the Federal Register and the Internal Revenue Bulletin.

​Temporary Regulations

Temporary regulations are published in the Federal Register; these are binding on taxpayers.

 I.R.C. § 7805(e) mandates that temporary regulations be issued concurrently as proposed regulations and, for regulations issued after November 20, 1988, that temporary regulations expire within 3 years of the date they are issued.

Final Regulations

Final regulations are published in the Federal Register and are ultimately in Title 26 of the C.F.R.. They are also published in the Internal Revenue Bulletin.

Final and proposed regulations are issued as Treasury Decisions before they are codified in the Code of Federal Regulations.  The Treasury Decisions contain explanatory preambles which are not included in the C.F.R

The official sources for Treasury regulations. The IRB is published weekly and cumulates semiannually as the CB. New regulations are listed as Treasury Decisions (TDs).

Standard Federal Tax Reporter & US Tax Reporter

Regulations are reprinted in both of these sets following the IRC section to which they relate. Recently adopted regulations are also included. In addition, the Standard Federal Tax Reporter reprints recent TDs in the U.S. Tax Cases Advance Sheets volume.

The Federal Register is the official daily publication for rules and notices of U.S. government agencies and organizations, as well as executive orders and other presidential documents.  The rules and notices are arranged chronologically, rather than by subject.

​Final Regulations ​are ultimately codified in title 26 of the C.F.R. the following are sources for accessing the CFR