Guides

Common IRS Notices and Letters: What They Mean and What To Do

A quick-reference guide to the IRS notices and letters you're most likely to receive—and what each one means for your next step.

Liam Williams

01 Mar 2026 — 9 min read

You opened an envelope from the IRS and there's a letter with a number on it—CP2000, Letter 566, CP504, or something else entirely. That number is the key to understanding what the IRS wants and how quickly you need to act.

This guide covers the most common IRS notices and letters. Find yours below to learn what it means, what your deadline is, and what happens if you do nothing.

How To Read Your IRS Notice

Every IRS notice includes a notice or letter number in the upper right corner of the first page. That number identifies the type of notice. The notice also includes a response deadline (if one applies), the tax year in question, and a phone number you can call with questions.

Keep the envelope. If a deadline ever becomes disputed, the postmark on the envelope can matter. And if your notice includes a response deadline, that date is measured from the date printed on the notice—not the day you received it.

Examination Notices

These notices relate to the IRS reviewing or adjusting your tax return—from automated matching programs through formal audits.

CP2000—Automated Underreporter

What it is: The IRS matched your return against income documents from employers, banks, and other payers (W-2s, 1099s, K-1s) and found a discrepancy. The CP2000 is a proposed adjustment—it explains what the IRS thinks you owe and why.

Deadline: 30 days from the notice date (60 days if you're outside the U.S.).

What to do: If you agree, sign and return the response form. If you disagree, check the box on the response form, explain why, and attach supporting documents.

If you ignore it: The IRS issues a Statutory Notice of Deficiency (CP3219A), which starts the 90 days clock to petition Tax Court.

The CP2000 is not a bill and not a Notice of Deficiency. It does not give the Tax Court jurisdiction over your case. But it is the easiest point in the process to resolve a discrepancy—responding now avoids a far more formal process later. Your Wage and Income transcript shows the same income documents the IRS used to generate the notice—comparing it to your return helps identify the discrepancy. See Tax Topic 652 for details.

Letter 566—Correspondence Audit

What it is: The IRS is auditing your return by mail. Letter 566 identifies the items under review and requests specific documents or information. This is the most common type of IRS audit.

Deadline: Typically 30 days from the letter date, though some variants allow 45 days. The exact deadline is stated on your letter.

What to do: Send copies (never originals) of the requested documents by the deadline. If you need more time, request a 30-day extension in writing before the deadline expires.

If you ignore it: The IRS disallows the items in question and sends an examination report—the 30-day letter described below.

For a complete walkthrough of the audit process—including your rights, what to bring, and how to respond—see How To Respond to an IRS Audit.

Letter 2205—Field Audit

What it is: Your return has been selected for an in-person examination. A revenue agent will contact you to schedule an appointment to review your records. This is a more intensive audit than a correspondence exam.

Deadline: The letter states a date to respond. The IRS allows 14 calendar days from mailing before following up by phone (IRM 4.46.3).

What to do: Call the revenue agent at the number on the letter to schedule the appointment. You can request that the examination take place at your representative's office if you have one.

If you ignore it: The agent follows up by phone, then by certified mail. Ultimately, the IRS prepares an examination report based on the information it already has—which almost always results in a larger adjustment than if you had participated.

30-Day Letter (Letter 525)—Examination Report

What it is: After completing its examination, the IRS sends you its proposed changes in an examination report along with a cover letter giving you 30 days to respond. This is commonly called the "30-day letter." It is your last chance to resolve the matter before the IRS issues a formal Notice of Deficiency.

Deadline: 30 days from the letter date.

What to do: If you agree, sign and return the agreement form. If you disagree, submit additional documentation with a written explanation—or request a conference with the IRS Independent Office of Appeals. Requesting Appeals gives you an independent review and often leads to settlement.

If you ignore it: The IRS issues a Notice of Deficiency (the 90-day letter), and the informal resolution window closes.

The 30-day letter is a fork in the road. Responding—especially by requesting Appeals—often leads to a negotiated outcome. Letting it pass means the next letter carries a hard, statutory deadline.

CP3219A / CP3219N—Notice of Deficiency

What it is: The formal, legal Notice of Deficiency—commonly called the "90-day letter." This is the IRS's official determination that you owe additional tax, sent by certified mail. CP3219A typically follows an automated underreporter case or correspondence exam. CP3219N is issued when the IRS files a substitute return for a non-filer. Both are governed by IRC § 6212.

Deadline: 90 days from the date on the notice (150 days if addressed to a person outside the United States). This deadline is set by IRC § 6213(a) and cannot be extended.

What to do: If you disagree, file a petition with the U.S. Tax Court through DAWSON before the deadline expires. The filing fee is $60. For disputes of $50,000 or less per tax year, you can elect small case (S case) procedures. See How To File Your Tax Court Petition for the full process.

If you ignore it: The IRS assesses the tax automatically after the deadline passes, and you lose your right to challenge it in Tax Court—the only court where you can dispute the amount before paying. Your remaining option is to pay the full amount and sue for a refund. See You Missed the 90-Day Deadline. Now What? for what happens next.

This notice is covered in depth in You Just Got a 90-Day Letter From the IRS. Here's What It Means.

Collection Notices

These notices are about money the IRS says you already owe. They follow a predictable escalation sequence over several months—from a first bill through warnings, liens, and levies.

CP14—Balance Due

What it is: The first balance-due notice. After your return is processed and the IRS determines you owe, CP14 is the formal "notice and demand for payment" required by IRC § 6303. It is the most frequently issued IRS notice.

Deadline: The notice requests payment within 21 days of the notice date.

What to do: If you can pay, pay online at IRS.gov/payments by the date on the notice to minimize interest and penalties. If you cannot pay in full, apply for a payment plan at IRS.gov/paymentplan. For balances under $50,000, you can set up a streamlined installment agreement online.

If you ignore it: Interest accrues from the original return due date, the late-payment penalty begins (0.5% per month, up to 25%), and the IRS sends CP501—the first in a series of increasingly urgent reminders.

If your notice includes penalties and you have a clean compliance history, you may be eligible for penalty relief. See How To Request IRS Penalty Abatement.

CP501 / CP503 / CP504—Balance Due Reminders

What they are: An escalating series of reminders if the balance from CP14 remains unpaid. The IRS sends these over a period of several months.

CP501 is the first reminder—a straightforward notice that the balance is still due.
CP503 is the second reminder, with stronger language warning that the IRS may file a Notice of Federal Tax Lien.
CP504 is a Notice of Intent to Levy under IRC § 6331(d). After CP504, the IRS can levy your state income tax refund.

Deadline: Each notice requests immediate payment.

What to do: The options are the same at every stage—pay, set up a payment plan, or contact the IRS if you disagree with the amount.

If you ignore them: After CP504, the next step is Letter 1058 / LT11—the final notice before the IRS can levy wages, bank accounts, and other property.

An important distinction: CP504 allows the IRS to seize your state tax refund, but it does not trigger Collection Due Process (CDP) hearing rights and does not authorize levy of other assets. Only Letter 1058 / LT11 does that. See the IRS CDP FAQ for confirmation.

Letter 1058 / LT11—Final Notice of Intent To Levy

What it is: The IRS's final notice before it can levy your wages, bank accounts, Social Security benefits, and other property. This notice satisfies the requirements of IRC § 6331(d) and triggers your right to a Collection Due Process hearing under IRC § 6330.

Deadline: 30 days from the day after the date on the notice to request a CDP hearing.

What to do: File Form 12153, Request for a Collection Due Process or Equivalent Hearing within the deadline. A timely CDP request pauses all collection activity, gives you a hearing before the IRS Independent Office of Appeals, and preserves your right to petition the Tax Court if you disagree with the outcome.

If you ignore it: The IRS can levy your wages, bank accounts, and other property. If you miss the 30 days CDP deadline, you can still request an equivalent hearing within one year—but collection continues and you lose Tax Court petition rights.

For a detailed walkthrough of the CDP process, see Collection Due Process Hearings: Your Right To Challenge IRS Liens and Levies.

Letter 3172—Notice of Federal Tax Lien

What it is: The IRS has filed a Notice of Federal Tax Lien (NFTL) with your local county recorder or state office, creating a public record of the government's claim against your property. Letter 3172 is the required notification to you under IRC § 6320. The federal tax lien itself arises automatically when tax is assessed, demand is sent, and payment is not made—the NFTL is the public filing that makes it enforceable against third parties under IRC § 6323.

Deadline: 30 days to request a CDP hearing.

What to do: File Form 12153 within the deadline. At the hearing, you can challenge whether the lien filing was appropriate, propose collection alternatives, or request a lien withdrawal.

If you ignore it: The lien remains as a public record, affecting your credit and your ability to sell or refinance property. The IRS may also proceed to levy action.

As with Letter 1058 / LT11, missing the 30 days deadline means you can request an equivalent hearing within one year but lose collection suspension and Tax Court rights. See Collection Due Process Hearings for a full explanation.

Other Notices

Not every IRS notice fits neatly into the examination or collection categories. These two come up frequently and have their own rules.

Letter 12C—Incomplete Return

What it is: The IRS received your return but cannot process it because something is missing, illegible, or inconsistent. This is not an audit—it is a processing issue. Common triggers include missing forms, unverifiable income or withholding, and missing Social Security numbers.

Deadline: 20 days from the date of the letter.

What to do: Read the letter carefully to identify exactly what information the IRS needs, then send only what is requested. Do not send a copy of your full return unless specifically asked, and do not file an amended return (Form 1040-X) in response.

If you ignore it: The IRS processes your return without the missing information, which typically means disallowed credits or deductions—and a smaller refund or a balance due.

See the IRS Letter 12C page for more detail.

Math Error Notice—Summary Assessment

What it is: The IRS found what it considers a "mathematical or clerical error" on your return and has already adjusted your tax and assessed the difference—without issuing a Notice of Deficiency first. This authority comes from IRC § 6213(b). Common math error notice numbers are CP11 (balance due), CP12 (refund changed), and CP13 (no change after adjustment).

Despite the name, "math error" authority extends beyond arithmetic mistakes. Under IRC § 6213(g), it covers inconsistent entries, missing required information, claims that exceed statutory limits, and incorrect taxpayer identification numbers.

Deadline: 60 days from the date of the notice to request abatement of the assessment.

What to do: If you disagree, request abatement in writing within 60 days. This is not optional if you want to preserve your rights—upon receiving a timely request, the IRS is required to reverse the assessment and follow normal deficiency procedures, which includes issuing a Notice of Deficiency that opens the door to Tax Court. Send the request by certified mail.

If you ignore it: The assessment becomes final. Because no Notice of Deficiency is issued, you lose access to Tax Court entirely. Your only remaining path is to pay the full amount and sue for a refund—a far more expensive and difficult process.

This is a trap for the unwary. Unlike the well-known 90 days deadline on a Notice of Deficiency, the 60-day math error abatement window gets little attention. Missing it is arguably worse because there is no fallback path to Tax Court. For more on how IRC § 6213 works, see How IRC 6213 Protects You While Your Tax Court Case Is Pending.

What If Your Notice Isn't Listed Here?

The IRS issues hundreds of different notices and letters. If yours isn't covered above, look up the notice number at IRS.gov/notices or call the phone number printed on your notice. If you need help understanding what a notice means or what to do about it, a Low Income Taxpayer Clinic can assist at no cost if you qualify.

Resources

This article is for informational purposes only and does not constitute legal or tax advice. For advice specific to your situation, consult a qualified tax professional or attorney.