Got an IRS Notice? What Each Common Letter Means

By Tom, CPA · Updated October 27, 2026

Part of: Tax Planning

TL;DR: Find the notice number, confirm it is real, compare it to your return, and respond in writing by the deadline. A CP2000 is a proposal you can dispute; a CP504 means act now.

Educational only, not tax, legal, or investment advice. Examples are illustrations, not predictions. Rules and limits change; verify current figures and talk to a qualified professional about your situation.

Few things raise a household's heart rate like an envelope from the Internal Revenue Service. It sits on the counter, radiating doom, while you wonder if you should open it or move to a cabin with no mailbox. Good news: most IRS letters are routine, many are resolved with a single reply, and the code printed in the top or bottom right corner tells you exactly what kind of letter it is. The tax code is 4 million words long; you need about 400 of them to decode the common notices.

This guide explains the CP2000, CP14, the CP501/503/504 series, Letter 5071C, and a step-by-step response process. It reflects IRS procedures as of Oct 2026. One important rule before anything else: the IRS generally initiates contact by mail. It does not demand payment by gift card, wire to a stranger, or threaten arrest by text. If a "notice" arrives that way, it is a scam.

CPA Warning Label: Deadlines on IRS notices can protect appeal rights. Respond in time, keep proof of mailing, and pay any agreed portion to stop interest.

First: find the notice number

Every IRS notice has a code, like CP2000 or LTR 5071C, usually in the top right or bottom right corner. Search it on the IRS "Understanding your IRS notice or letter" page to see an explanation and sample. Also note:

• The tax year it concerns.
• The response deadline. Deadlines matter because missing them can escalate the issue or forfeit appeal rights.
• The amount claimed, if any.
• Whether it asks you to do something or is just informational.

Verify it is real. You can log into your IRS Online Account at irs.gov to see balances and many notices. If the letter's balance does not appear in your account, call the number on IRS.gov, not just the number on the letter.

CP2000: the underreported income proposal

The CP2000 is not an audit bill. It is a proposal. The IRS's automated matching system compared your return with information returns (W-2s, 1099s, 1098s, brokerage reports) and found a mismatch. The notice proposes changes to your tax, often with interest and possibly an accuracy penalty.

Common causes:

• A forgotten 1099-INT or 1099-DIV from a small account.
• A brokerage 1099-B where the cost basis was not reported to the IRS, making the entire sale proceeds look like gain.
• A 1099-R for a rollover that was not marked as a rollover on the return.
• A 1099-NEC or 1099-K for freelance or platform income.
• A late corrected form from a payer.

Response options are on the notice's response form: agree and pay (or arrange a payment plan), partially agree, or disagree with an explanation and documents. If you disagree, send proof: the basis statement, the rollover deposit, the corrected 1099. You usually have 30 days from the notice date, and you can call to request more time.

A CP2000 is a great time to discover your broker's basis reporting was incomplete. In many cases, the "income" the IRS sees shrinks dramatically once basis is shown.

CP14: you have a balance due

The CP14 is the first bill. It says you owe tax, usually because the return showed a balance that was not paid in full, or because of an adjustment. It includes the tax, penalties and interest to date.

If the amount is correct, pay by the date shown to stop further penalties and interest from growing. Options include IRS Direct Pay, the Electronic Federal Tax Payment System, debit or credit card (with processing fees), or a payment plan. The IRS offers short-term payment plans and long-term installment agreements, often set up online.

If it is wrong, for example you paid but the payment was applied to the wrong year, call the number on the notice with your payment confirmation.

Penalty and interest details are covered in our IRS penalties guide.

CP501, CP503 and CP504: the reminder escalation

If a CP14 balance goes unpaid, reminders follow:

After a CP504, the IRS can move toward further collection steps. Before levying wages or bank accounts, it generally must send a final notice of intent to levy with a right to a Collection Due Process hearing (commonly Letter 1058 or LT11). That hearing request has a strict 30-day deadline.

Ignoring the reminder series makes everything worse: the failure-to-pay penalty rate increases after a notice of intent to levy, and collection options narrow. The IRS is usually willing to set up payment plans with people who engage.

Letter 5071C: prove you are you

Letter 5071C says the IRS received a return with your name and Social Security number and needs to verify your identity before processing it. It is an identity theft protection step, not an accusation.

• If you filed the return, verify your identity using the method in the letter, typically the IRS identity verification service online or by phone. Have the letter, the return in question and the prior year's return handy.
• If you did not file a return, report that through the same process. It may indicate identity theft, and the IRS has a process to resolve it. An Identity Protection PIN for future years is a good idea.

Refunds are held until verification is complete. Responding quickly is the fastest way to get your refund released. Related letters (4883C, 5747C) have similar purposes with different verification methods.

Other letters you might see

• CP11 / CP12: the IRS changed your return, often a math error or a miscalculated credit. CP11 means you owe because of the change; CP12 means your refund changed. You can usually ask for the change to be reversed within 60 days if you disagree.
• CP59: the IRS has no record of a return it expected from you. File it, or explain why none was required.
• CP90 / Letter 1058: final notice of intent to levy with Collection Due Process rights. Treat as urgent.
• Letter 566 or 2205: an audit is starting. See our audit guide.
• CP2501: an earlier-stage mismatch inquiry asking for an explanation before a formal CP2000.

Not sure which bucket a letter falls in? The IRS notice lookup page has samples for hundreds of codes.

Response steps that work

1. Do not panic, do not ignore. Open it the day it arrives.
2. Confirm it is real via your IRS Online Account or the official phone number.
3. Compare to your return. Pull the return for that year and the documents behind it.
4. Decide: agree, partially agree, or disagree.
5. Respond in writing by the deadline, using the response form. Include copies, never originals. Write your name, SSN and tax year on each page.
6. Keep proof of when you responded: certified mail receipt, fax confirmation, or upload confirmation if the notice offers an online option.
7. Pay what you agree you owe, even while disputing the rest, to stop interest on that part.
8. Follow up. IRS processing of correspondence can take months. Note the date and check your online account.
9. Get help if it is complex or large. The Taxpayer Advocate Service, an independent office in the IRS, helps people facing hardship or stuck processes, free.

Illustration: a CP2000 that shrinks

Pat receives a CP2000 for 2024 proposing $4,100 of additional tax plus interest. The notice lists a 1099-B showing $22,000 of stock sale proceeds that Pat omitted. Pat's broker did not report cost basis because the shares were bought long ago. Pat finds the purchase records: basis was $19,500, held more than a year, so the real long-term gain was $2,500.

Pat checks "disagree" on the response form, attaches a completed Form 8949 showing proceeds, basis and gain, and a copy of the purchase confirmation. At Pat's 15% long-term capital gains rate, the corrected tax is about $375, plus interest. Pat pays that amount with the response to stop interest on the agreed portion. Months later, a revised notice confirms the lower amount. Illustrative only.