The IRS’s National Office issues Private Letter Rulings, also called “Letter Rulings,” in response to a taxpayer’s request for the IRS’s interpretations of the IRC and regulations regarding a particular situation (usually a prospective transaction). Letter Rulings are not binding on the IRS and cannot be cited as precedent. However, private letter rulings issued after October 31, 1976 may be relied on as substantial authority to avoid the substantial understatement penalty. They are numbered by the year, week and order of issuance (e.g., LTR 923242 indicates the 42nd ruling issued in the 32nd week of 1992).
Available on Westlaw from 1950-present.
Available on Lexis Advance from 1954-current.