In addition to "IRB Guidance", the IRS regularly drafts other forms of administrative decision-making. They are not published in the Internal Revenue Bulletin.
Private Letter Rulings:
A private letter ruling is the result of a request by a taxpayer to the Office of Chief Counsel for guidance on a proposed transaction. A PLR is binding only between the requesting taxpayer and the IRS. PLRs issued after October 31, 1976 may be considered as substantial authority.
Technical Advice Memoranda:
A Technical Advice Memorandum is issued either at the IRS's or the taxpayer's request for Chief Counsel guidance on a complex issue arising during the audit or examination of a particular taxpayer. A TAM is binding only on the particular taxpayer. TAMs issued after October 31, 1976 may be considered as substantial authority.
Chief Counsel Advice:
Chief Counsel Advice consists of memoranda written in response to various internal requests for guidance from IRS agents, officers, and attorneys. Chief Counsel Advice is not substantial authority and cannot be cited in court.
FTX-CCA (chief counsel advice); FTX-PLR (private letter rulings); FTX-TAM (technical advice memoranda); FTX-WD (all written determinations).
IRS Private Letter Rulings, IRS Technical Advice Memoranda databases.
"Agency Decisions" link leads to databases for all the different types of Chief Counsel Advice.
IRS Forms and Publications:
The Internal Revenue Manual:
Available from the IRS's website: www.irs.gov/irm/index.html
Available from the IRS's website