What Is the Internal Revenue Code?
The Internal Revenue Code (IRC) is the statutory body of law that governs federal taxation in the United States. It is formally codified as Title 26 of the United States Code (26 U.S.C.). The current version is officially titled the Internal Revenue Code of 1986 — though it has been amended thousands of times since then, including major overhauls in 1993, 2001, 2003, 2010, 2017 (Tax Cuts and Jobs Act), and 2022 (Inflation Reduction Act).
The IRC is enacted by Congress through legislation, interpreted and enforced by the Internal Revenue Service (IRS), and reviewed by the Tax Court, federal district courts, and ultimately the Supreme Court when disputes arise.
📑 The IRC vs. IRS Regulations
The IRC is the law itself. The IRS issues Treasury Regulations (26 C.F.R.) that interpret the law, plus Revenue Rulings, Revenue Procedures, Notices, and Private Letter Rulings that provide additional guidance. When they're in conflict, the IRC controls.
▶ What Is the Purpose of the Internal Revenue Code?
The Tax Museum • Educational overview of the IRC's purpose and structure
How to Read an IRC Citation
Legal citations to the IRC follow a specific format. Understanding this format lets you look up any provision directly.
The alternative citation format is 26 U.S.C. § 61(a)(1) — both refer to the same provision. When reading tax literature, news, or legal documents, you'll see both formats used interchangeably.
The 11 Subtitles of the IRC: A to K
The IRC is divided into 11 Subtitles, each covering a distinct category of federal tax law:
- Subtitle A — Income Taxes: The largest and most important subtitle. Covers all income taxes for individuals (Chapter 1), self-employment taxes (Chapter 2), withholding (Chapter 3), real estate investment trusts, regulated investment companies, insurance companies, S corporations, partnerships, trusts, and estates.
- Subtitle B — Estate and Gift Taxes: Federal estate tax (Chapter 11), gift taxes (Chapter 12), and generation-skipping transfer taxes (Chapter 13). Includes the current $13.61 million per-person estate tax exemption (2024).
- Subtitle C — Employment Taxes: Social Security and Medicare taxes (FICA), federal unemployment taxes (FUTA), Railroad Retirement taxes, and income tax withholding requirements for employers.
- Subtitle D — Miscellaneous Excise Taxes: Excise taxes on retail sales of heavy trucks, ship passengers, air transportation, indoor tanning services, certain health insurance policies (Cadillac tax), and more.
- Subtitle E — Alcohol, Tobacco, and Certain Other Excise Taxes: Detailed production, importation, and distribution tax rules for distilled spirits, wines, beer, tobacco products, and firearms.
- Subtitle F — Procedure and Administration: How the IRS assesses and collects taxes, statute of limitations, penalties and interest, Tax Court procedures, audits, collections due process, and the Taxpayer Bill of Rights.
- Subtitle G — Joint Committee on Taxation: Establishes the bipartisan congressional tax oversight committee.
- Subtitle H — Financing of Presidential Election Campaigns: Rules for the $3 Presidential Election Campaign Fund checkoff on Form 1040.
- Subtitle I — Trust Fund Code: Rules for the Highway Trust Fund and other federal trust funds.
- Subtitle J — Coal Industry Health Benefits: Healthcare funding provisions for retired coal miners and their beneficiaries.
- Subtitle K — Group Health Plan Requirements: COBRA continuation coverage, health flexible spending accounts, and employer group health plan rules.
The Most Important IRC Sections for Individual Taxpayers
Out of thousands of sections, these are the ones most relevant to the average American individual taxpayer:
| Section | Topic | What It Does |
|---|---|---|
| §1 | Tax rates | Establishes the individual income tax rate brackets (10% through 37%) |
| §61 | Gross income defined | Defines gross income as "all income from whatever source derived" — the broadest possible definition |
| §63 | Taxable income | Defines taxable income as gross income minus deductions; establishes the standard deduction |
| §71-86 | Specific inclusions | What counts as income: alimony (pre-2019), prizes, annuities, Social Security, discharge of debt, etc. |
| §101-140 | Exclusions from income | What is NOT taxed: life insurance proceeds, gifts & inheritances, municipal bond interest, employer health benefits |
| §151-153 | Personal exemptions | Rules for dependent exemptions (modified by TCJA) |
| §161-249 | Deductions | All allowable deductions for individuals and businesses |
| §213 | Medical expenses | Deduction for medical expenses above 7.5% of AGI |
| §163 | Interest deduction | Mortgage interest deduction rules and investment interest |
| §170 | Charitable deductions | Rules for deducting charitable contributions to qualifying organizations |
| §21 | Child care credit | Credit for dependent care expenses |
| §24 | Child tax credit | $2,000 per qualifying child; up to $1,700 refundable |
| §32 | Earned income credit | Refundable credit for low-to-moderate income workers |
| §401 | Qualified retirement plans | Rules for 401(k), profit-sharing, and other employer retirement plans |
| §408 | Individual Retirement Accounts | Traditional and Roth IRA contribution and distribution rules |
| §6012 | Who must file | Requirements for who must file a federal income tax return |
| §6072 | Filing deadline | April 15 deadline for individual returns (or next business day) |
How to Look Up the IRC
The full text of the IRC is available for free from multiple official and semi-official sources:
- Cornell Law School LII — The most user-friendly interface. Browse by subtitle, chapter, section. Updated promptly when Congress acts.
- US House of Representatives (uscode.house.gov) — The official government source. Can download entire title as PDF.
- IRS.gov — Revenue Rulings, Procedures, Notices, and other guidance interpreting the IRC.
- Government Publishing Office (govinfo.gov) — Official printed version; also available as XML/bulk download for researchers.
📖 How to Search Effectively
When looking for a specific rule, try searching "IRC § [topic] site:law.cornell.edu" in Google. For example: "IRC deduction home office site:law.cornell.edu". You can also search directly within the Cornell LII site for keywords like "home office," "capital gains," or any tax term.