CHAPTER I—INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY
- SUBCHAPTER A—INCOME TAX (Parts 1–19)
- SUBCHAPTER B—ESTATE AND GIFT TAXES (Parts 20–27)
- SUBCHAPTER C—EMPLOYMENT TAXES AND COLLECTION OF INCOME TAX AT SOURCE (Parts 30–37)
- SUBCHAPTER D—MISCELLANEOUS EXCISE TAXES (Parts 40–158)
- SUBCHAPTER F—PROCEDURE AND ADMINISTRATION (Parts 300–421)
- SUBCHAPTER G—REGULATIONS UNDER TAX CONVENTIONS (Parts 500–521)
- SUBCHAPTER H—INTERNAL REVENUE PRACTICE (Parts 600–802)