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Federal Income Tax Research Guide: Primary Sources

Guide to Federal Income Tax research.

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Internal Revenue Code

The Internal Revenue Code (I.R.C.), enacted in Title 26 of the U.S. Code, is the foundation of federal tax law. The following resources provide annotated versions of the code:

Annotated codes are useful because they provide commentary on code sections and citations to other primary law (such as cases, regulations, and guidance documents). For a quick tour of annotated codes on Bloomberg Tax, VitalLaw, and Checkpoint, see the videos to the right.

Treasury Regulations

Treasury Regulations, codified in Title 26 of the Code of Federal Regulations (C.F.R), interpret and expand upon the Internal Revenue Code.

I.R.B. Guidance

The Internal Revenue Bulletin (I.R.B.) is the I.R.S.'s instrument for announcing official rulings and procedures, as well as other notices, announcements, and items of interest tax professionals.

  • Revenue Rulings are the I.R.S.'s official interpretations of the Internal Revenue Code and Treasury Regulations, as well as other relevant statutes, treaties, and regulations.
  • Revenue Procedures are the I.R.S.'s official statements of tax procedure.

Written Determinations

Other administrative documents promulgated by the I.R.S. include:

  • Private Letter Rulings
    • Statements made at the request of taxpayers that explain the I.R.S.'s interpretation of the law as applied to specific fact patterns.
  • Technical Advice Memoranda
    • Statements made at the request of taxpayers that provide guidance on technical and procedural questions.

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