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In general, when doing US federal tax research, the Internal Revenue Code (IRC) has priority. After the IRC, researchers tend to look at the IRS regulations. The IRS also issues many administrative materials and pronouncements which have the force of law, such as Revenue Rulings and Letter Rulings, which may apply to all taxpayers or only to a particular taxpayer. Cases and other resources (such as secondary sources) are used to interpret the code, regulations, and IRS pronouncements.
Use a tax research guide (see listed below) to famiarize yourself with the major tax documents, their abbreviations, and where they can be found. If you have access be sure to use the tax resources in online databases such as Lexis, Westlaw, CCH, BNA, RIA, and IBFD.
U.S. Supreme Court & Acquiescence
Only decisions by the U.S. Supreme Court are binding authority on the IRS. For decisions from other courts in which the IRS does not prevail, the Commissioner must decide whether to abandon its position in the litigation (acquiescence) or to continue to pursue the IRS’s position in subsequent litigation (non-acquiescence). Tax citators and databases such as Lexis, Westlaw, CCH, and RIA include information on these decisions.
Federal Appellate Courts
Tax opinions from the U.S. Circuit Courts of Appeals and Court of Appeals for the Federal Circuit are published in the Federal Reporter series. West's Federal Claims Reporter (formerly United States Claims Court Reporter) includes opinions from the Court of Appeals for the Federal Circuit and the Supreme Court.
In order of precedential value, the Tax Court issues regular decisions (published), memorandum decisions (unpublished), and summary decisions. The official opinions are published in the United States Tax Court Reports (TC). Before 1942, when the Tax Court was called the Board of Tax Appeals, the official reporter was the Board of Tax Appeal Reports. These official reporters as well as memorandum decisions are available in databases such as Lexis, Westlaw, CCH, BNA, and in the HeinOnline Federal Agency Library. All decisions from the Tax Court are available since 1995 on the Tax Court web site.
Federal District Courts
Tax opinions are published along with other federal district court opinions, in West’s Federal Supplement (since 1932) and Federal Reporter (before 1932). Westlaw contains PDF images of all cases reported in these sources.
Court of Federal Claims
Between Oct. 1, 1982, and Oct. 29, 1992, this court was called the United States Claims Court. Before that, it was known as the United States Court of Claims and only the Supreme Court had jurisdiction over appeals from its decisions. Court of Federal Claims decisions are published in the U.S. Court of Claims Reports, West's United States Claims Court Reporter (1982-1991), and West’s Federal Claims Reporter (1992- ).
The major tax research databases and looseleaf services publish nearly all of these cases, plus additional district court cases not reported in F. Supp. These resources are sometimes the only source of some federal district court opinions on taxation. Opinions for all these courts are collected and published by CCH in U.S. Tax Cases (U.S.T.C.) (LOOSELEAFS) and by the Research Institute of America (RIA) in American Federal Tax Reports (A.F.T.R., A.F.T.R. 2d). (LOOSELEAFS).