An audit letter is not a bill, and it is not a verdict. It is the start of a defined process with defined deadlines — and almost every bad audit outcome traces back to a missed deadline or an ignored letter, not to the audit itself. This page is the map for the whole cluster: identify your audit from the letter in front of you, see the process every audit follows, and find the page that owns your exact situation.
General information, not tax or legal advice. Audit deadlines are short and unforgiving; if your case involves large amounts, a business, or a fraud allegation, get an attorney, CPA or enrolled agent involved before you respond.
One reassurance first: the IRS notifies you of an audit by mail only — it never initiates an audit by telephone. A caller claiming you are “under audit” and demanding payment is not the IRS. A real audit always begins with a letter.
The number printed on your letter tells you where you are in the process and which page you need:
| What you received | What it means | Your page |
|---|---|---|
| Notice CP75 (or CP75A / CP75D) | A mail audit of your credits, dependents or income has opened; part of your refund is held | CP75 guide |
| A first letter asking for documents on one or a few items (Letter 566 series) | A correspondence audit has opened | Correspondence audit |
| A letter setting an appointment, often with Form 4564 (Information Document Request) | An office or field audit | Office & field audits |
| Letter 525 (mail exams) or Letter 915 (office/field) with Form 4549 enclosed | The exam is done and changes are proposed — you have 30 days to agree, send proof, or appeal | Letter 525 guide |
| CP3219N / Letter 3219 — the Statutory Notice of Deficiency (“90-day letter”) | The Appeals door has closed; only a Tax Court petition remains | Tax Court petition |
| A tax bill for an audit you never answered, or one already closed | The assessment is made — but a closed audit can sometimes be reopened | Audit reconsideration |
Whatever the type, the sequence is the same (IRS Publication 3498, Rev. 5-2025, is the IRS’s own current walkthrough of it):
Correspondence audit. The most common type: handled entirely by mail from an IRS campus, usually one tax year and one or a few issues — a credit, a deduction, a mismatch. No examiner is assigned to you personally, and silence automatically advances the case against you. Full playbook: correspondence audit.
Office audit. You (or your representative) meet a Tax Compliance Officer at an IRS office, bringing the records listed in the IRS’s written request. Usually individual returns with a defined set of issues.
Field audit. A Revenue Agent comes to your home, your place of business, or your representative’s office. Field exams are the broadest — typically businesses and complex returns — and the agent can probe income itself, including bank-deposit analysis. Both in-person types, side by side: office & field audits.
You may handle an audit yourself or be represented by an attorney, CPA, or enrolled agent; with a power of attorney on file, the representative can deal with the IRS in your place. The Taxpayer Bill of Rights (Publication 1, sent with your first notice) guarantees, among other things, the right to challenge the IRS’s position and be heard, and the right to appeal an IRS decision in an independent forum. If cost is the barrier, Low Income Taxpayer Clinics and the Taxpayer Advocate Service help eligible taxpayers for free or a nominal fee — see our guide to free IRS tax help and Low Income Taxpayer Clinics.
Prepare before you write anything: the response itself, done properly, is a page of its own — how to respond to an IRS audit letter — and the records that win each issue are in the record-keeping checklist. Why returns get picked at all: what triggers an IRS audit. Disagree with a finished exam? The Appeals process end-to-end is here: appealing an audit to the Office of Appeals.
What happens during an IRS audit? The IRS examines specific items on your return and asks you to substantiate them with records — by mail or in an interview. It ends with no change, an agreed change you sign, or an unagreed change you can appeal to the Independent Office of Appeals and then take to Tax Court (Schwab’s explainer and IRS Publication 3498 both lay the sequence out this way).
What should I do if I get audited by the IRS? Read the letter to identify the type and the deadline, gather exactly the documents requested — copies, never originals — and respond within the window given, even if the response is a request for more time (the AARP Foundation’s audit guidance starts from the same three steps). Never ignore the letter: silence moves the case forward without you.
What if I need more time to respond? Ask before the deadline. For a mail audit, fax a written extension request to the number on your letter (or mail it); for an office or field audit, call the examiner. The IRS’s own audits page lists requesting more time as a standard option — but the request has to arrive before the date passes.
Can someone represent me at an IRS audit? Yes. An attorney, CPA or enrolled agent can represent you, and with a signed power of attorney they can attend meetings and deal with the IRS on your behalf — in an office or field audit, in your place (FindLaw’s representation guidance covers the mechanics).
Sources: IRS.gov — “IRS audits,” “Understanding your CP75 notice,” IRS Publications 3498 (Rev. 5-2025), 3498-A, 556 and 1; Taxpayer Advocate Service. Currency verified 2026-10-23.