The Internal Revenue Code (IRC) is Title 26 of the United States Code , and the related regulations are Title 26 of the Code of Federal Regulations. You can find these in print and electronically with all versions of the US Code and Code of Federal Regulations (see "United States Code" and/or "Code of Federal Regulations).
The IRC and related regs are also published as free-standing paperback volumes (from CCH and RIA), as CD-ROMs, and they are included in most online tax databases, including Tax Analysts' Federal Research Library, RIA's CheckPoint and the electronic edition of the CCH Standard Federal Tax Reporter on Intelliconnect.
You can also get the Code and Regs as part of the United States Code and the Code of Federal Regulations, respectively. This is particularly useful because there are reliable, free Internet editions of the USC and CFR (see "United States Code" and "Code of Federal Regulations").
To see if or when a section of the tax code was amended look in the annotations following the text. For recent changes to the tax code, look in the annotations to the text on Lexis or Westlaw, or search a database of Public Laws. For regulations, you could also check the annotations to the text on Lexis or Westlaw, or you could search the Federal Register or look through the List of CFR Sections Affected.
Historical Editions: Some larger law libraries keep volumes of the Code & Regs back many years, and you can find old Codes and Regs in historical editions of the USC and CFR (see the "Historical Editions" section of the United States Code and Code of Federal Regulations entries). Also, there is a multi-volume set called Cumulative Changes in the Internal Revenue Code of 1954 and Tax Regulations Under the Code that covers 1954 through 1985. Westlaw's "Internal Revenue Code of 1954" lets you search the Code as it existed before the Tax Reform Act of 1986 (FTX-IRC-54). Checkpoint has historical editions of the Code back to 1990, plus preambles to Proposed and Final Regs back to 1975 (subscription).
Legislative History: The legislative history of Federal tax laws is similar to the legislative history of other laws. See the Federal Legislative History entry for general information. In addition, you can find tax legislative history materials published in the following sets.
- Seidman's Legislative History of Federal Income Tax Laws, 1938-1861 (The Lawbook Exchange);
- Seidman's Legislative History of Federal Income and Excess Profits Tax Laws, 1953-1939 (Prentice Hall);
- A Guide and Analytical Index to the Internal Revenue Acts of the United States, 1909-1950 (W.S. Hein & Co.);
- Legislative History of Federal Income and Excess Profits Tax Laws, 1953-1939 (Prentice Hall);
- Internal Revenue Acts: Text and Legislative History (West) from 1954 on; and
- Tax Management -- Primary Sources (BNA) from 1969 on.
Lexis offers a database of tax bills, laws and selected Congressional Reports going back to 1954 (FEDTAX;LEGIS). The Westlaw equivalent goes back to 1948 (FTX-LH), with a special file for the Tax Reform Act of 1986 (FTX-TRA86). RIA's CheckPoint has Reports for tax bills back to the 104th Congress, i.e., 1994-1995 (Federal Library / Federal Source Materials Pending and Enacted Legislation). Tax Analysts' Federal Research Library has legislative history materials back 1981.
The U.S. Federal Legislative History collection on HeinOnline is a good source for legislative histories of older tax laws including the two Seidman's Legislative History books mentioned above, the four-volume Legislative History of the United States Tax Conventions, which covers tax treaties up to about 2010, and several legislative histories for individual tax laws.
Conference Reports are published in the IRS's Cumulative Bulletins (see "Internal Revenue Service"). They sometimes come as freebies for subscribers to the multi-volume tax treatises.
If there is one, look at the "Bluebook" and any other report by the staff of the Joint Committee on Taxation to explain major tax laws after they are passed. Blue Books are posted from 1969 on the JCT Web site, and many law libraries keep the old editions published by the GPO and CCH. You can search through old editions of the Blue Book from 1970 on Lexis (FEDTAX;JCTBB) and from 1976 on Westlaw (FTX-JCS).
Tax legislative history materials are also available in all the general legislative history sources discussed in the "Federal Legislative History" entry.
Public comments on Regs: For recent comments, check Regulations.gov. If that doesn't work, you can try Tax Notes Today through the Federal Research Library, Lexis (TAXANA;TNT) or Westlaw (TNT). For older comments call the IRS library and see if they can help. If not, you might have to file a FOIA request with the IRS.