What Happens During an IRS Audit? A Calm, Clear Walkthrough

Quick answer: An IRS audit is a review of your tax return to check that income, deductions, and credits were reported correctly — most are handled entirely by mail and focus on just one or two items, not your entire financial life. The process runs through a notice, a document exchange, a review, and a resolution, and it typically takes several months from start to finish. You have the right to representation at every step, and responding accurately and on time is the single biggest factor in how smoothly it goes.

Key takeaways

The IRS selects returns for audit through computer scoring, random selection, and matching against forms filed by employers and banks, according to the IRS's own description of its audit selection process.
Most individual audits are correspondence audits conducted by mail, not in-person meetings — the IRS states these make up the large majority of exams.
You generally have 30 days to respond to an audit notice, though the IRS will consider a written request for more time.
The IRS's own three-year lookback rule for assessing additional tax extends to six years if income was substantially underreported, and there's no time limit if a return was never filed or fraud is involved.

Step 1: Understand Why You're Being Contacted

If you're being audited, the IRS will tell you by mail — first. The IRS is explicit that it initiates audits by mail, never by phone, email, or text, and any message claiming otherwise should be treated as a scam. The notice will name the tax year in question and usually the specific items being examined, such as a business expense deduction, a reported income figure, or a claimed credit.

Audits get triggered a few common ways:

Automated scoring — the IRS uses a system that flags returns where deductions or credits look unusual compared to similar filers.
Document mismatches — a W-2 or 1099 filed by an employer or bank doesn't match what you reported.
Related examinations — a business partner, investor, or related entity is already being audited.
Random selection — a small percentage of returns are chosen without any red flag at all.

Knowing which category you fall into matters less than knowing this: an audit notice is not an accusation of wrongdoing. It's a request to substantiate what's already on the return.

Step 2: Read the Notice Carefully and Confirm What's Being Asked

Every IRS notice has a letter or notice number in the corner, and that number tells you exactly what kind of audit you're facing. This distinction shapes your entire next move:

Audit type	How it happens	What it typically covers
Correspondence audit	Entirely by mail	One or two specific items (a deduction, a credit, unreported income)
Office audit	In-person at an IRS office	Multiple items, more detailed records
Field audit	IRS agent visits your home or business	Complex returns, business filings, broader scope

Correspondence audits are the most common by far, and they're also the least stressful — you're mailing or uploading documents, not sitting across a table from an examiner. Whatever type you're dealing with, the notice will list a response deadline. The IRS generally gives 30 days, and it does allow taxpayers to request additional time in writing if they need it.

Don't skip this: Missing the response deadline doesn't make the audit go away — it lets the IRS adjust your return based on the information it already has, which almost always favors the government's position, not yours.

Step 3: Gather Documentation Before You Respond

The IRS will only accept records that support what you actually claimed on the return, so pulling the right documents matters more than pulling a lot of documents. If the audit concerns a business deduction, you need proof the expense happened and that it was for business use. If it concerns income, you need proof of what you actually received and from whom.

Checklist — documents to gather before responding to an audit notice:

Locate the original tax return and any schedules tied to the flagged item.
Pull bank and credit card statements covering the tax year in question.
Collect receipts, invoices, or contracts backing up deductions claimed.
Gather mileage logs or vehicle records if a transportation deduction is involved.
Find W-2s, 1099s, and K-1s and compare them line by line to what was filed.
Retrieve prior correspondence if this isn't the first notice on this issue.
Make copies of everything — never send the IRS your only original.
Note the notice number and response deadline somewhere visible.

If you're missing records because a return was late or never filed in the first place, that's a separate problem worth solving first — we walk through it in How to File Back Taxes: A Step-by-Step Walkthrough. An audit and an unfiled return are two different situations, and mixing them up during a response only slows things down.

Step 4: Decide How You'll Respond — And Whether You Need Representation

You can respond to an audit yourself, but you're also entitled to have someone represent you, and the IRS's own Taxpayer Bill of Rights guarantees this. That representative can be a CPA, an enrolled agent, or an attorney, and once you authorize one, the IRS can communicate directly with them instead of you.

Representation tends to matter most in a few specific situations:

The audit covers business income, since business returns usually involve more moving pieces than a simple W-2 return.
More than one tax year is under review.
The notice mentions a substantial understatement of income rather than a single line-item question.
You're self-employed and the deductions being questioned span a full Schedule C — a scenario we cover in more depth in Self-Employed Tax Preparation: What to Expect Your First Year.
You disagree with the IRS's position and expect to need to appeal.

For a straightforward correspondence audit questioning one deduction with clear paper backup, many taxpayers handle it directly. For anything broader, having someone who deals with the IRS regularly review your response before it's mailed can catch mistakes that turn a one-round exchange into a three-round one.

Step 5: Submit Your Response and Wait for the IRS Review

Once you mail or upload your documents, the IRS examiner reviews them against your return and decides one of three things: your original figures were correct, some adjustment is needed, or more information is required. This step is largely out of your hands — the waiting is normal, and it can run from a few weeks to several months depending on the complexity of the case and current IRS processing volume.

During this stage:

Keep copies of everything you sent and the date you sent it.
Respond promptly if the IRS asks a follow-up question — don't let a second request go unanswered just because you already sent something once.
Don't assume silence means it's resolved. No news is just no news yet.

Step 6: Understand the Outcome and Your Options

An audit ends in one of three ways, and each one has a clear next step. The IRS explains all three in the notice it sends closing out the exam:

No change — your return was accepted as filed, and the audit is closed with no further action needed.
Agreed adjustment — you and the IRS agree on a change, you sign the examination report, and you pay any additional tax, penalties, and interest owed (or arrange payment).
Disagreed adjustment — you don't accept the proposed change, and you have the right to request a conference with an IRS manager or file a formal appeal with the IRS Independent Office of Appeals.

If the outcome includes penalties, know that penalty relief is sometimes available depending on your history and the reason for the issue — a topic we cover fully in Understanding IRS Penalty Relief: Your Options Explained. Penalties for the same error aren't always automatic or permanent, and it's worth knowing what relief categories exist before assuming a bill is final.

What to Do Next

If a notice just arrived in your mailbox, don't respond in a panic and don't ignore it either. Read it fully, note the deadline, and start gathering the specific records it references — that alone puts you ahead of most people who receive one.

If the return under review was prepared without professional help, or if you're unsure whether your documentation actually supports what was claimed, it's worth having a second set of eyes look at both the notice and the original return before you send anything back. USTAXX Consulting Services works with individuals and business owners across Illinois and nationwide on exactly this kind of IRS correspondence, and founding preparer Akmammet's team has handled cases ranging from a single questioned deduction to multi-year business exams.

If you've received an audit notice and want a clear read on what it's really asking for, reach out to USTAXX Consulting Services — a short conversation now can save weeks of back-and-forth later.