What Happens During the IRS Audit Process?

Most people picture an IRS audit as a dramatic, confrontational event. The reality is different. An audit is a structured administrative process with defined stages, specific documents at each stage, and fixed deadlines between them. Understanding the sequence is the first step in navigating it calmly. This chapter walks through what actually happens during an IRS audit — start to finish — with examples drawn from cases we have handled.

Our firm has represented taxpayers in hundreds of audits as IRS audit defense counsel. The descriptions that follow are drawn from that practice: what notices arrive, what examiners ask, how information is exchanged, when the tempo matters, and what the final documents mean. For context on why a return was selected, see Why the IRS Audits Tax Returns. For the strategic framework, see IRS Audit Strategy.

The Four Stages of the IRS Audit Process

Every audit moves through the same four stages, regardless of type. What differs is the duration of each stage, the volume of documents exchanged, and the stakes of the adjustments proposed.

1. Stage 1: Notice — How the Audit Begins

Stage 1 is the moment the IRS issues formal notice that the taxpayer has been selected for examination. The notice identifies the audit type, the tax year under review, the specific items being examined, and the deadline to respond. Everything that follows is triggered by this letter.

Audit notices arrive by U.S. Mail, never by phone or email. The IRS’s initial contact on any audit is always in writing. Common audit notices include the CP2000 (automated underreporter mismatch), Letter 566 (correspondence substantiation request), Letter 915 or 3572 (office audit scheduling), Letter 2205-A or 2205-B (field audit), and Notice 1214 or Letter 3121 (NRP research audit).

The notice includes four critical pieces of information: the tax year under examination, the specific items being questioned, the response deadline, and the contact information for the assigned examiner. The taxpayer should read the notice carefully for each.

An important point for context: the notice rarely tells the taxpayer why the return was selected. The DIF algorithm, the AUR match, the related-party referral — none of these are typically disclosed in the initial letter. The examiner may not know either. What the notice does disclose is the scope, and that disclosure is what determines the response.

Stage 1 Procedure

1. Photograph the envelope. Postmark controls deadline calculation.
2. Read the notice in full. Identify audit type, year, scope, and deadline.
3. Calendar the deadline in two places. The missed-deadline error is the most common procedural loss.
4. Do not call the IRS yet. The contact record opens the moment the call is answered.
5. Engage counsel for intake. A 15-minute call confirms audit type, severity, and representation scope.

2. Stage 2: Information Exchange — IDRs and Meetings

Stage 2 is the period during which the IRS examiner gathers evidence to evaluate the return’s positions. Information flows through two channels: Information Document Requests (IDRs) that ask for specific records, and interviews or meetings where the examiner asks questions directly. This is the longest stage of most audits.³

An Information Document Request is a formal written request for specific categories of records. Typical IDR categories on a Schedule C audit include gross receipts substantiation (bank statements and deposit records), cost-of-goods-sold records, fixed asset schedules and depreciation support, the general ledger, underlying invoices and receipts for a sampled list of expenses, and the accounting software backup file. The IDR lists each category with a response deadline, usually 15 to 45 days.

Meetings and interviews occur in office and field audits. An office audit is typically a single meeting of two to four hours at an IRS Taxpayer Assistance Center. A field audit involves multiple visits by the Revenue Agent, usually at the taxpayer’s business, spanning weeks or months. Under IRC §7521, the taxpayer has the right to have a representative attend any meeting and to consult that representative before answering off-scope questions.

In our experience, Stage 2 is where most audit outcomes are actually decided. The records produced and the answers given here become the examiner’s working file. By the time Stage 3 arrives, the proposed adjustments are largely baked in.

Stage 2 Procedure

1. Map each IDR line item to a named folder. Mixed-category gathering produces disorganized responses that widen audits.
2. Reconcile records to the return. Every deduction should tie, dollar for dollar, to substantiation.
3. Produce only what was requested. Extra records invite scope expansion.
4. Route responses through the representative. No direct taxpayer submissions to the examiner.
5. Request extensions in writing before the deadline. Most examiners grant one or two extensions.
6. Document the examiner’s questions. A contemporaneous memorandum of each meeting protects the record.
7. Pause when new issues surface. IRC §7521(b)(2) protects the right to consult before answering.

3. Stage 3: Proposed Adjustments — The Examination Report

Stage 3 is the period during which the examiner drafts and issues a report proposing adjustments to the return. The report arrives as Form 4549 (Income Tax Examination Changes) accompanied by Form 886-A (Explanation of Items). Together they show what the examiner proposes to change, the dollar impact, and the reasoning.⁴

A typical Form 4549 includes a line-item breakdown of each adjustment (added income, disallowed deductions, denied credits), the resulting change in taxable income, the recomputed tax, and any penalties proposed. Penalties commonly appear in three tiers: the 20% accuracy-related penalty under IRC §6662, the 40% substantial-understatement penalty, and the 75% civil fraud penalty under §6663. Each penalty has specific elements the IRS must prove, and each has specific defenses the taxpayer can raise.

Form 886-A is the examiner’s written rationale. It cites the IRS position on each issue, the Code sections and regulations involved, and the documents the examiner relied on. A thorough 886-A makes the taxpayer’s position at Appeals easier; a thin or error-prone 886-A is itself a point of attack.

Before Form 4549 is finalized, the examiner typically holds a closing conference with the taxpayer and representative. This is the final opportunity to present defenses, offer additional substantiation, or negotiate adjustments before the report issues. Closing conferences frequently result in measurable reductions when well prepared.

Stage 3 Strategy

1. Review Form 4549 line by line. Arithmetic errors are common.
2. Cross-check against Form 886-A. Each proposed adjustment should be supported by stated facts and cited law.
3. Identify penalty defenses. Reasonable cause under §6664(c), professional reliance under Boyle, and substantial authority under §6662(d) are the primary defenses.
4. Prepare for the closing conference. Written responses, supporting exhibits, alternative calculations.
5. Do not sign the report at the conference. Request the full 30-day review period.

4. Stage 4: Closeout — Agreement, Appeals, or Tax Court

Stage 4 is the period from the examination report through final resolution. The taxpayer has three paths: agree and close the case (sign Form 4549 or Form 870), request IRS Appeals, or petition the U.S. Tax Court after receiving the Notice of Deficiency. Each path has different procedural rules, costs, and timelines.

The closeout documents and their effects:

• Form 870 (Waiver of Restrictions on Assessment). Agreement to the proposed adjustments. Generally precludes Tax Court but does not waive refund claims.
• Letter 525 (30-Day Letter). Formal notice of proposed changes with the right to protest to Appeals within 30 days.
• Notice CP3219A or Letter 3219 (Statutory Notice of Deficiency / 90-Day Letter). The final notice before assessment. The taxpayer has 90 days (150 if addressed abroad) to petition Tax Court. The deadline is jurisdictional.
• Form 872 (Consent to Extend Statute). Voluntary extension of the assessment period. Strategic decision; never sign without counsel.

The Appeals path is administrative, costs nothing to initiate, and resolves approximately 85% of cases that reach it. Appeals Officers apply a “hazards of litigation” analysis and have authority to settle at any percentage of the proposed adjustment. The Tax Court path is judicial — a formal petition, docketed case, and tax liability not collectable until the court rules.

How Far Back Can the Audit Reach? The Statute of Limitations

The statute of limitations under IRC §6501 defines how far back the examiner can go. The limits shape the scope of every audit.

• 3 years (standard rule). The IRS has 3 years from the filing date or due date (whichever is later) to assess. Most correspondence and office audits operate within this window.
• 6 years (substantial omission). When more than 25% of gross income is omitted — or more than $5,000 of foreign financial asset income — the window extends to 6 years.
• No statute (fraud or unfiled). When fraud is proven, or when a return was never filed, the statute is open indefinitely. The IRS can reach any year.
• Form 872 extensions. The taxpayer can consent to extend the statute. This is a strategic decision. Extensions sometimes benefit the taxpayer and sometimes only the IRS.

Field audits frequently expand backward as the examiner finds patterns. An audit that opens on Year X often adds Years X-1 and X-2 once unreported income or significant adjustments appear. Counsel should be involved in every Form 872 decision.

Audit Process by Type: Timing and Scope

The four audit types move through the same four stages but at very different tempos. The table below summarizes typical duration and scope by type.

Appeals adds another 6 to 12 months. A Tax Court petition, when necessary, adds 1 to 2 years. A fully contested field audit with Appeals and Tax Court litigation can span 4 to 5 years.

The Audit Escalation Pathway

Audits do not always stay at the level they started. Understanding escalation triggers is the difference between a managed process and a cascading one.

Correspondence to Office or Field

Escalation occurs when the taxpayer’s response to a correspondence audit reveals broader issues, when submitted documents show patterns the original flag did not capture, or when indicia of fraud (duplicate books, altered documents, unexplained cash) surface during examiner review. Roughly 15% of correspondence audits escalate; the other 85% close at correspondence level.

Office to Field

Office audits escalate when the Tax Compliance Officer reaches the limits of their authority — multi-entity structures, significant business complexity, or on-site inspection needs. Once referred to field, the case stays at field.

Field to Criminal Investigation

Field audits escalate to Criminal Investigation when a Revenue Agent identifies firm indications of fraud under IRM Part 25.1.2. Indicators include consistent patterns of unreported income, false statements during the audit, concealment of assets, and obstructive behavior. Criminal acceptance pauses the civil audit; civil strategy becomes secondary.

The escalation pathway is the reason each stage matters. A clean Stage 2 response keeps the audit narrow and prevents Stage 3 from expanding; a precise Stage 3 negotiation positions the taxpayer for a favorable Stage 4 outcome.

The First 48 Hours After an Audit Notice

The first two days after the notice arrives shape the outcome of the entire process. The sequence below reflects what we recommend to every new client.

1. Do not call the IRS yet. The number on the notice connects to an examiner. Statements become part of the file.
2. Photograph the envelope. The postmark, not the delivery date, starts the deadline clock.
3. Identify the letter code. Reference the lookup table above.
4. Verify the notice is legitimate. Genuine IRS notices include an IRS address, a notice or letter number in the upper right, and never threaten arrest or demand payment in gift cards or cryptocurrency.
5. Calendar the response deadline in two places. The missed-deadline error is the most common procedural loss.
6. Do not pull documents yet. Gathering records before scope is clear risks producing more than required.
7. Engage a tax attorney for an intake call. A Form 2848 Power of Attorney redirects IRS contact to the representative.

When to Engage an Attorney for an Audit

Not every audit warrants counsel at Stage 1. A $2,000 CP2000 for a missing 1099 that can be documented in 20 minutes does not. The situations below are the ones where the cost of self-representation almost always exceeds the fee for counsel.

• Field audit (Letter 2205-A or 2205-B). Field audits should not be handled without representation. The initial interview alone shapes the trajectory of the case.
• Proposed deficiency above $10,000. The ROI calculation favors counsel almost every time.
• Business returns (Schedule C, S-corp, partnership). Scope expands quickly without representation.
• Any penalty language on the report. Penalty defenses must be preserved at Appeals or are typically waived.
• Bank deposit analysis questions. The civil-to-criminal pivot point.
• Audit expanding mid-examination. Stop the bleeding with representation.
• Notice of Deficiency received. The 90-day petition window is jurisdictional.

Frequently Asked Questions

Next Steps in This Guide

The appropriate next chapter depends on where in the process you are.

• To identify which audit type you have: The 4 Types of IRS Audits.
• To understand how returns are selected: Why the IRS Audits Tax Returns.
• To build a response framework: IRS Audit Strategy.
• To reduce future audit risk: IRS Audit Red Flags & Risk Reduction.
• If the audit has concluded and the result is in dispute: Appealing an IRS Audit.
• To engage representation: IRS Audit Defense Attorney.

If you would prefer to have someone walk through your specific notice with you, a 15-minute consultation is free. We will identify the stage, explain what happens next, and give you a candid assessment.