Taxation Research: Agency Documents

TD Treasury Decisions (final and temporary tax regulations; authoritative)

PR Proposed regulations (not authoritative)

RP Revenue procedures (statements of IRS practices and procedures; authoritative)

RR Revenue Rulings (rulings applying the law to particular facts presented by a taxpayer; authoritative for same factual circumstances unless officially revoked) Also available from TaxLinks, beginning with 1954: (http://www.taxlinks.com/)

LR Letter rulings (limited authoritative value)

PLR Private Letter Rulings are usually requested from the IRS National Office by a taxpayer before a transaction is completed

TAM Technical Advice Memoranda concern completed transactions and are issued by the IRS’s National Office, usually at the request of an agent during an audit (http://www.irs.gov/app/picklist/list/writtenDeterminations.html)

GCM General Counsel Memoranda are usually issued at the request of the IRS to assist in the preparation of Revenue Rulings and Private Letter Rulings (for those made public by the IRS, see http://www.irs.gov/foia/article/0,,id=103756,00.html)

AOD Actions on Decisions are prepared when the IRS loses a case in court. The AOD recommends what action the IRS should take. (http://www.irs.gov/app/picklist/list/actionsOnDecisions.html)

TM Technical Memoranda examine final regulations.

Interpretive Guidance may also be found in:
i. Determination Letters: similar to PLRs, but issued by the office of the local IRS district director
ii. IRS News Releases (http://www.irs.gov/newsroom/article/0,,id=108500,00.html)
iii. IRS Announcements & Notices: published in Federal Register; IRB. Notices, but not Announcements, also appear in the CB. 
iv. Acquiescences and Nonacquiescences are issued when the decision in a case is adverse to the IRS and indicates whether the IRS will follow the decision in cases other than that of the specific taxpayer. Published in IRB;CB
v. Internal Revenue Manual (http://www.irs.gov/irm/)
vi. IRS Forms and Instructions (http://www.irs.gov/formspubs/index.html)
vii. Chief Counsel Memoranda
viii. Miscellaneous Publications