The IRC has had three major amendments: the 1939 Code, the 1954 Code, and the 1986 Code. Prior to the 1939 Code, federal tax laws were enacted in individual revenue acts.

Internal Revenue Code of 1986

• Pub. Law 99-514, 100 Stat. 2985, Oct. 22, 1986
• Current IRC, 26 U.S. Code with amendments

Internal Revenue Code of 1954

• Ch. 736, 68A Stat. 3, Aug. 16, 1954

Internal Revenue Code of 1939

• Ch. 2, 53 Stat. 1, February 10, 1939

Cite to the Internal Revenue Code, instead of the U.S. Code.  Example:  I.R.C. § 61. 

Bluebook rule 12.9.1

Organized with all provisions on a sub-topic usually found together with numerous cross-references to related sections.

It is useful to scan the table of contents for a chapter to get an idea of the overall structure of a topic.