Quick overview

When the IRS sends a notice or letter it will usually cite one or more Internal Revenue Code (IRC) sections. Those citations tell you the legal rule the IRS says applies — for example, what counts as income, which deductions are allowed, or why a penalty was assessed. Treat the citation as a roadmap: it points to the issue, but you still must read the rest of the notice and gather the documents the IRS requests.

In my 15+ years helping clients respond to IRS notices, I’ve found that understanding the few sections that come up repeatedly (and what the IRS expects) shortens the dispute process and increases the chance of a favorable result.

(This article explains the commonly cited sections, how to read them in notices, practical steps to respond, and where to look for authoritative guidance. It is educational and does not replace tailored tax advice.)

Why the IRS includes code citations in notices

A citation to an IRC section gives the legal basis for the IRS’s position. Examples:

  • To show what the agency considers “gross income” (Section 61).
  • To explain allowable business expenses (Section 162).
  • To justify disallowing a charitable deduction (Section 170).

Citations help you and any representative you hire find the statutory rule quickly. The IRS expects taxpayers to act on the information in the notice: respond by the deadline, supply requested records, or follow the appeal steps. See the IRS guidance on notices and correspondence for procedural details (IRS.gov).

Common IRC sections you’ll see on individual and business notices (plain English)

Below are frequently cited code sections, what they mean in simple terms, and practical actions to take if a notice references them.

  • Section 61 — Gross income defined

  • Plain English: Everything you receive in money, property, or services is taxable unless the law says it isn’t.

  • Why it appears: Used in notices about unreported income (third-party data mismatches, 1099s, wages, prizes, or barter income).

  • Action: Compare the IRS’s figures to your records (W-2s, 1099s, bank deposits). If you disagree, provide proof like pay stubs, 1099 corrections, or a ledger.

  • Source: IRC §61; general treatment found at irs.gov and Cornell Law School’s Legal Information Institute.

  • Section 162 — Trade or business expenses

  • Plain English: Allows ordinary and necessary expenses paid or incurred in carrying on a trade or business.

  • Why it appears: When the IRS questions whether amounts you deducted are business-related.

  • Action: Provide invoices, receipts, mileage logs, contracts, or a profit-loss statement showing the business purpose.

  • Section 170 — Charitable contributions

  • Plain English: Explains when donations to qualified organizations are deductible and how much you can deduct.

  • Why it appears: In notices denying or adjusting charitable deduction claims.

  • Action: Supply receipts, written acknowledgments from charities, bank records, and Form 8283 for noncash gifts over threshold amounts.

  • Reference: See IRS Publication 526 for substantiation rules (irs.gov).

  • Section 179 — Election to expense certain depreciable business property

  • Plain English: Lets small businesses elect to deduct the cost of qualifying equipment in the year placed in service instead of depreciating over time.

  • Why it appears: Inquiries about eligibility, limits, or whether an asset was placed in service.

  • Action: Provide purchase records, date placed in service, business use logs, and depreciation schedules.

  • Section 351 — Transfers to corporation controlled by transferor

  • Plain English: When someone transfers property to a corporation and controls it after the transfer, they generally don’t recognize gain immediately.

  • Why it appears: Notices involving incorporations, reorganizations, or stock transfers.

  • Action: Provide documentation of transfers, stock issuances, and the ownership structure at the time of transfer.

  • Sections commonly tied to penalties and procedural issues

  • Section 6651 — Failure to file or pay

    • Plain English: Explains penalties for not filing returns or paying taxes on time.
    • Action: If you missed a deadline, supply evidence of reasonable cause (illness, disaster, reliance on incorrect advice) and ask for penalty abatement.

  • Section 6695/6694 — Preparer penalties

    • Plain English: Rules that can penalize tax return preparers for negligent or fraudulent returns.
    • Action: If a preparer error is alleged, communicate with the preparer and consider substitution of representation.

How to read the IRS notice with a cited code section

  1. Read the notice headline and the cited section(s). The agency usually summarizes the issue in plain language near the top.
  2. Check the numeric adjustment lines (where they show amounts added or removed) and match them to your return.
  3. Collect documents that directly address the IRS’s legal claim (e.g., receipts for deductions, corrected 1099s, bills of sale).
  4. Note any deadline and the contact information for the IRS unit that issued the notice.

If the notice cites a statute you don’t understand, look it up on irs.gov or Cornell LII to read the exact text. Treat statutory language as the legal rule and IRS notices as the agency’s application of that rule to your case.

Practical checklist: documents to prepare by issue type

  • Unreported income (Section 61): W-2s, 1099s, bank statements, evidence of nontaxable receipts.
  • Disallowed business expense (Section 162): Receipts, mileage logs, contracts, proof of business activity (invoices, client agreements).
  • Charitable deduction issues (Section 170): Charity receipts, written acknowledgments, canceled checks, Form 8283 for large noncash gifts.
  • Property/equipment disputes (Section 179): Purchase invoice, proof of business use, depreciation schedule.

Real-world examples and a short case study

Example 1 — Underreported freelance income: A client (freelance designer) received a notice showing a 1099-MISC payment that wasn’t on his return (IRC §61 cited). We gathered his invoicing records, a corrected 1099 from the payer, and bank deposit records; the IRS adjusted the notice and removed the assessed tax.

Example 2 — Disallowed charitable deduction: A client claimed a large noncash donation without the required Form 8283 and written acknowledgment (IRC §170). We collected the charity’s acknowledgment and a qualified appraisal; the deduction was accepted after an amended return.

My practice note: Timely and well-organized documentation frequently resolves simple citation disputes without the need for appeals.

Common mistakes taxpayers make

  • Responding emotionally rather than with documents — always prioritize records over arguments.
  • Sending incomplete substantiation — the IRS looks for specific items (dates, amounts, payee/recipient).
  • Missing deadlines — many notices include short response windows; follow them to preserve appeal rights.

Steps to take if you disagree

  1. Don’t ignore the notice. Read it and calendar the deadline.
  2. Gather documents tied directly to the cited section and issue.
  3. If the notice requests an amended return and you agree, file it promptly. If you disagree, send a clear written response with supporting evidence and a cover letter.
  4. If you prefer professional help, consider an enrolled agent, CPA, or tax attorney. If you hire representation, you’ll typically provide a signed Form 2848 (Power of Attorney) to allow the representative to communicate with the IRS on your behalf.

See our guide on the anatomy of IRS notices for help reading deadlines and contact lines: The Anatomy of an IRS Notice: Reading Codes, Deadlines, and Contact Info.

Also useful: Decoding IRS Notice Codes: A Practical Checklist for Taxpayers.

If your issue involves audit-style code citations, see our deeper article: Understanding Tax Code Sections Commonly Used in Audits.

Authoritative sources and where to look

  • Internal Revenue Service (IRS) — for procedures, forms, and publications: irs.gov. For notice procedures and common publications, see IRS Publications such as Publication 1, Publication 17, Publication 526, and forms instructions.
  • Internal Revenue Code (text) — available via government sources and Cornell Law School’s Legal Information Institute for readable statutory language.
  • U.S. Department of the Treasury — for regulatory guidance.

Final tips

  • Keep good records year-round: receipts, bank statements, mileage logs, and contracts make notice responses quick and effective.
  • When in doubt, document first and argue later. Evidence that directly addresses a cited code section wins most routine disputes.

Professional disclaimer: This article is educational and reflects general practices as of 2025. It does not constitute legal, tax, or accounting advice for your specific situation. Consult a qualified tax professional to get personalized help.

Sources: Internal Revenue Service (irs.gov), Internal Revenue Code (via Cornell LII), IRS publications noted above.