IRS Publication 556: Examination of Returns, Appeal Rights, and Claims for Refund
Receiving an IRS audit notice is one of the most stressful experiences a taxpayer can face. Publication 556 is your guide to the entire examination process — from understanding why your return was selected to exercising your appeal rights and, if necessary, filing a claim for refund. Knowing your rights and the critical deadlines can mean the difference between a manageable resolution and a devastating tax bill.
Types of IRS Audits — What to Expect
Correspondence Audit
The most common type. Handled entirely by mail, typically for straightforward issues such as missing W-2s, 1099s, math errors, or discrepancies between reported income and information returns. The IRS sends a letter requesting documentation — you respond by mail with the requested records. Most correspondence audits are resolved without an in-person meeting.
Office Audit
Conducted at a local IRS office. You receive a letter scheduling an appointment and listing the specific records to bring. Office audits usually focus on specific items on the return, such as deductions, credits, or rental income. You have the right to bring your attorney, CPA, or enrolled agent to represent you.
Field Audit
The most comprehensive and intrusive type. An IRS revenue agent visits your home, place of business, or your representative's office. Field audits are typically reserved for complex returns — business returns, high-income individuals, or cases involving multiple related entities. The agent conducts a thorough review of books, records, and underlying documentation.
Taxpayer Compliance Measurement Program (TCMP) Audit
A research audit where the IRS examines every line of the return in exhaustive detail to update its DIF scoring formulas. These are rare but extremely burdensome — the IRS uses the data to improve audit selection, not necessarily because your return raised any red flags. Full documentation is required for every item on the return.
Information Document Request (IDR)
During any audit, the examiner may issue an IDR — a formal, written request for specific documents, records, or explanations. You have a right to understand the purpose of each request. Responding completely and on time is critical; failure to respond can lead to a summons and potential penalties.
How the IRS Selects Returns for Audit
The IRS uses several methods to identify returns for examination. Understanding how your return may have been flagged can help you prepare a stronger defense.
DIF Scoring (Discriminant Function System)
The IRS computers score every return using secret statistical formulas (DIF) that compare your deductions, credits, and income against national norms. Returns with unusually high scores are flagged for manual review. The IRS does not disclose the DIF formula.
Related Examinations
If you were a partner in a partnership, a shareholder in an S corporation, or involved in a tax shelter that is under audit, your individual return may be pulled for examination even if it would not otherwise have been flagged. The IRS coordinates these related-party audits.
Information Matching
The IRS matches the income reported on your return against W-2s, 1099s, and 1098s filed by employers, banks, and other payers. If the information does not match, your return is flagged for a correspondence audit. The IRS's Automated Underreporter (AUR) program handles most of these cases.
Market Segment Specialization Program (MSSP)
The IRS maintains audit technique guides for specific industries and professions — real estate, construction, legal, medical, and more. Returns in targeted industries may be selected for audit based on industry-specific red flags identified in MSSP guides.
Statute of Limitations — Timing Is Everything
The IRS does not have unlimited time to examine your return or assess additional tax. These deadlines are governed by the statute of limitations under IRC Section 6501.
General Rule: 3 Years
The IRS generally has 3 years from the later of the due date of the return or the date you actually filed to assess additional tax. For most individual returns, this means the assessment period expires 3 years after April 15 (or the actual filing date if filed late). After this period, the IRS cannot assess additional tax for that year.
Substantial Understatement: 6 Years
If you omit more than 25% of your gross income from the return, the assessment period extends to 6 years. This applies to substantial understatements of income — the IRS gets double the time to assess the additional tax.
Fraud or No Return Filed: Unlimited
If you file a fraudulent return, or if you never file a return at all, there is NO statute of limitations. The IRS can assess tax at any time, no matter how many years have passed. Civil fraud penalties can reach 75% of the underpayment.
Extending the Statute by Agreement
The IRS may ask you to sign Form 872, Consent to Extend the Time to Assess Tax. You are not required to sign it. However, if you do not sign and the statute is about to expire, the IRS may issue a Statutory Notice of Deficiency based on the information it has — which may be unfavorable to you. Carefully consider whether an extension is in your interest before agreeing.
Your Rights During an IRS Examination
The IRS Taxpayer Bill of Rights guarantees specific protections during an audit. You have the right to:
Professional Representation
You may represent yourself, or you may be represented by an attorney, CPA, or enrolled agent. You do not have to meet with the IRS alone — you can have your representative attend all meetings in your place (with a valid Power of Attorney, Form 2848).
Recording the Examination
You may make an audio recording of the interview if you provide the IRS with 10 days' advance written notice. The IRS also has the right to record the interview, but must notify you in advance.
Know Why the IRS Is Asking
The IRS must explain why it is requesting specific information and how the information relates to the examination. You have the right to understand the purpose of every Information Document Request (IDR).
Appeal and Judicial Review
You have the right to appeal any IRS decision to the IRS Independent Office of Appeals and, ultimately, to the courts — including the U.S. Tax Court, U.S. District Court, or U.S. Court of Federal Claims.
Not to Be Harassed
The IRS cannot contact you at unreasonable times or locations. Examinations should be conducted during normal business hours and should not involve unnecessary visits, calls, or excessive document requests designed solely to pressure you into conceding.
The 30-Day Letter and 90-Day Letter — Understanding the Notices
If the IRS examiner proposes changes to your return that you do not agree with, a sequence of formal notices begins. The deadlines attached to these notices are absolute — missing them can permanently limit your options.
The 30-Day Letter
After the examination concludes, if you do not agree with the examiner's proposed changes, the IRS sends a 30-day letter — a formal report summarizing the proposed adjustments. You have 30 days from the date of this letter to request a conference with the IRS Independent Office of Appeals. The 30-day letter is not a bill; it is an invitation to appeal before a final assessment is made. You should respond in writing, explaining why you disagree and requesting an appeals conference.
The 90-Day Letter (Statutory Notice of Deficiency)
If you do not respond to the 30-day letter, or if the Appeals Office sustains the proposed changes, the IRS issues a 90-day letter — formally called a Statutory Notice of Deficiency. This is the IRS's final determination that you owe additional tax. You have EXACTLY 90 days from the date printed on the notice (not the date you receive it) to file a petition with the U.S. Tax Court. This is a jurisdictional deadline set by law — there are no extensions, no exceptions, and the Tax Court cannot grant relief for late filings. If you miss this deadline, the IRS will assess the tax and begin collection. You can still pay the tax and sue for a refund in District Court or the Court of Federal Claims, but you lose access to the Tax Court (which does not require you to pay the tax first).
Appealing to the IRS Independent Office of Appeals
The IRS Independent Office of Appeals is a separate organization within the IRS that resolves disputes without litigation. Appeals officers are independent of the examining agent and have the authority to settle cases based on litigation hazards — if the IRS is likely to lose in court, Appeals can settle.
Small Case Request ($25K or Less)
If the total proposed additional tax and penalties for any one tax period is $25,000 or less, you can use the simplified small case request procedure. You do not need to file a formal written protest — a letter stating the changes you disagree with and the reasons is sufficient. The small case procedure is faster, less formal, and often resolved at the appeals conference itself.
Formal Written Protest ($25K+)
For disputes exceeding $25,000 per tax period, you must file a formal written protest. The protest must include: (1) your name, address, and a statement that you want to appeal; (2) a copy of the examination report showing the proposed changes; (3) the tax periods or years involved; (4) a list of each change you disagree with and why; (5) the facts supporting your position on each disputed issue; and (6) the law or authority you are relying on. The protest must be signed under penalties of perjury.
The Appeals Conference
The appeals conference is an informal meeting where the appeals officer reviews the facts and law with you or your representative. Appeals officers are trained to evaluate the hazards of litigation — meaning they will consider how likely the IRS is to win if the case goes to court. Many cases settle at this stage. If you reach an agreement, you sign a Form 870, Waiver of Restrictions on Assessment, and the case is closed.
No Agreement? Going to Tax Court
If you cannot reach an agreement with the Appeals Office, or if you chose to bypass Appeals and go directly to court, you must petition the U.S. Tax Court within 90 days of the date on the Statutory Notice of Deficiency. The Tax Court does not require you to pay the disputed tax before hearing your case — this is a major advantage over District Court, which requires full payment first.
Filing a Claim for Refund — Getting Your Money Back
If you believe you overpaid your tax, or if you paid the tax after an audit and later discovered grounds for a refund, Publication 556 explains how to file a claim for refund. The process is separate from the appeals process — you are asking the IRS to return money you already paid.
Form 1040-X — Amended U.S. Individual Income Tax Return
The primary form for claiming a refund of individual income tax. You must generally file within 3 years from the date you filed your original return, or within 2 years from the date you paid the tax — whichever is later. Each tax year requires a separate Form 1040-X. You must explain in detail why you are entitled to the refund and attach supporting documentation.
Form 843 — Claim for Refund and Request for Abatement
Used to claim a refund of certain taxes other than income tax, or to request abatement of interest and penalties due to IRS error or delay. Also used for certain employment taxes, excise taxes, and estate or gift taxes that were overpaid.
Protective Claims
A protective claim preserves your right to a refund while you wait for the outcome of a related matter — such as pending litigation, a related-party audit, or legislation that may affect your liability. Filing a protective claim stops the refund statute of limitations from expiring while the related matter is resolved.
If Your Refund Claim Is Denied
If the IRS denies your claim for refund (or does not act on it within 6 months), you may file suit in the U.S. District Court or the U.S. Court of Federal Claims. Unlike Tax Court, you must have paid the tax in full before you can sue for a refund. The statute of limitations for filing a refund suit is generally 2 years from the date the IRS mails the notice of disallowance.
Critical Deadlines — Do Not Miss These
30-Day Letter Response
You have 30 days from the date on the exam report to request an appeals conference. Missing this deadline does not foreclose appeal — the IRS will issue a 90-day letter next, restarting the process — but it delays resolution and can limit settlement flexibility.
90-Day Tax Court Petition
90 days from the date on the Statutory Notice of Deficiency to file a Tax Court petition. THIS IS A JURISDICTIONAL DEADLINE. No extensions. No exceptions. If you miss it, you lose Tax Court access permanently for that tax year.
Refund Claim: 3 Years
You generally have 3 years from the date you filed your original return, or 2 years from the date you paid the tax — whichever is later — to file a claim for refund. After this period, even a valid overpayment becomes the government's money.
Assessment Statute: 3 Years
The IRS generally has 3 years from filing to assess additional tax. If the statute is about to expire and you are in the middle of an audit, the IRS may ask you to sign Form 872 to extend the period. Consult a tax professional before signing any extension.
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