The U.S. Treasury Department issues three kinds of regulations that interpret and clarify sections of the Internal Revenue Code (IRC).
Final and proposed treasury regulations are first issued as Treasury Decisions (T.D.) using a sequential numbering system that does not indicate the year of issue or relevant IRC section. Treasury Decisions are important because they contain a preamble, which provides insight into the purpose, effect, and operation of the regulation. The preamble is reprinted in the Federal Register but does not accompany temporary and final regulations when they are published in the Code of Federal Regulations (CFR). Likewise, the looseleaf services typically do not publish preambles.
When temporary and final treasury regulations are published in the CFR, they follow a standard numbering scheme consisting of three parts. The number before the decimal indicates the the type of tax (e.g. 1 for income, 20 for estate & gift, 31 for employment, etc.). The number following the decimal corresponds to the relevant IRC section. The number after the dash is a sequential numbering scheme. Thus, Treas. Reg. § 1.167(a)-1 is the first income tax regulation interpreting code section 167(a).
Research Tip: Remember that the IRC is amended frequently, often a dozen times in one year. When a code section changes, the existing regulations that relate to it may become inconsistent with the section's language. When you are working with a regulation, always make sure that it is consistent with the current IRC section before relying on it. The looseleaf services do a good job of alerting the researcher to these inconsistencies.
The following are some sources for locating treasury regulations:
IRS rulings apply the law to specific facts presented by taxpayers.
Since 1953, rulings that the IRS considers to be of general interest are officially published as Revenue Rulings (Rev. Rul.). They are less authoritative than regulations but do have precedential value for others in essentially the same circumstances. They are published in the Internal Revenue Bulletin as well as the resources listed at the end of this section.
Revenue rulings are assigned numbers chronologically by year in this format YY-## (up to 2000) or YYYY-## (2000 and later). For example, Rev. Rul. 90-10 represents the 10th revenue ruling issued in 1990, and Rev. Rul. 2002-5 is the fifth revenue ruling issued in 2002.
Note: Revenue rulings can be revoked or modified. You can check their status using citators (e.g. Shepard’s or tables in looseleaf services on federal taxation).
Private letter rulings (or letter rulings) (P.L.R.; PLR; Ltr. Rul.; Priv. Ltr. Rul.) are those IRS rulings on individual taxpayer questions that the IRS does not deem to be of general interest. These rulings are not officially published, nor do they have precedential authority, although they can offer insight into IRS policy.
Private letter rulings are numbered with the following information: year of ruling (two digits though 1999 and then four digits), week of ruling (two digits), and a number chronologically assigned as each ruling is issued that week (three digits). For example, PLR 9325039 is the 39th private letter ruling issued in the 25th week of 1993, and PLR 200005003 is the third private letter ruling issued in the fifth week of the year 2000.
Revenue rulings and private letter rulings can be found in:
