Internal Revenue Bulletin
The IRS produces a dizzying array of administrative material. The Internal Revenue Bulletin "is the authoritative instrument for announcing official rulings and procedures of the IRS and for publishing Treasury Decisions, Executive Orders, Tax Conventions, legislation, court decisions, and other items of general interest." Between 1919 and 2008 this material was collected in the twice-yearly Cumulative Bulletin.
Internal Revenue Manual (Describes how the IRS is organized and how it operates.)
Other useful IRS information
The Office of Tax Policy develops and implements tax policies and programs, reviews regulations and rulings to administer the Internal Revenue Code, negotiates tax treaties, provides economic and legal policy analysis for domestic and international tax policy decisions, and provides estimates for the President's budget, fiscal policy decisions, and cash management decisions." (U.S. Treasury website)
The United States Tax Court is a court of record established by Congress under Article I of the U.S. Constitution. When the Commissioner of Internal Revenue has determined a tax deficiency, the taxpayer may dispute the deficiency in the Tax Court before paying any disputed amount.
The Congressional Budget Office. "Since 1975, CBO has produced independent analyses of budgetary and economic issues to support the Congressional budget process." (CBO Website) The CBO Website offers: