Generally, primary sources of federal law are documents issued by a branch of the federal government or by a federal agency. When providing support for a  position, primary sources carry more weight of authority than secondary sources.

With respect to federal tax law, primary sources that carry a high weight of authority include the following:

  • Internal Revenue Code
  • Other non-codified Federal tax statutes
  • Final and temporary regulations
  • Judicial decisions on tax matters
  • Revenue Rulings
  • Revenue Procedures
  • Other published IRS Positions (e.g., Notices and Announcements)

Primary sources that provide guidance but should not be cited as legal authority include the following:

  • Proposed regulations (unless they are specifically earmarked as "reliance regulations")
  • Legislative history (e.g., Committee Reports)
  • IRS Letter Rulings may be relied on by recipient of ruling)
    • Private Letter Rulings
    • Determinations letters
    • Technical Advice Memorandum
    • Chief Counsel Advice
  • IRS internal documents made available to the public
    • Internal Revenue Manual
    • Audit Technique Guides
    • Actions on Decisions
  • Taxpayer assistance
    • IRS Publications
    • Federal tax forms and form instructions
    • IRS Frequently Asked Questions and Answers

Secondary Sources

Secondary sources are publications written by legal analysts, scholars, and other tax professionals. There are numerous secondary sources available, including the following:

  • Tax law reporters published by commercial tax research services
  • Treatises
  • Articles in legal periodicals
  • Textbooks
  • Newsletters

Commercial services, such as CCH AnswerConnect, are heavily used in tax practice because they are comprehensive, updated frequently, and explain the rules in plain English. When beginning federal tax research, starting with a commercial service can save time because the research materials provide an overview of a particular tax topic, along with summaries of and links to full text of primary sources.