If you’re wondering why the IRS would send you a letter, the short answer is that the agency contacts taxpayers by mail for a handful of predictable reasons: it corrected a mistake on your return, the income you reported doesn’t match what employers or banks reported, you’re missing a document, your identity needs to be verified, you owe a balance, or a return is being audited. Every notice has a number printed in the upper right corner, starting with “CP” or “LTR,” and that number tells you exactly what the letter is about and what you need to do.
Find the Notice Number First
Before anything else, look at the upper right corner of the letter. The notice number (something like CP11, CP2000, CP14, or a letter code such as 5071C) identifies the specific reason the IRS wrote to you. You can search that number on the IRS website to see the standard explanation, or log in to your IRS Online Account, where legitimate notices appear in your file.1Internal Revenue Service. Understanding Your IRS Notice or Letter2Internal Revenue Service. Online Account for Individuals
Most letters ask for one specific thing and give you a deadline. Read the whole letter before reacting. The reasons below cover the great majority of what the IRS actually sends.
The IRS Corrected Your Return
One of the most common letters simply tells you the IRS found and fixed a mistake. These are sometimes called math error notices, and they carry designations like CP11, CP12, or CP13. The IRS doesn’t need to run a formal audit for these adjustments; it has authority to fix calculation errors, correct a filing status, or adjust credits that don’t line up with supporting data, and then send you a notice explaining the change.
A CP11 means the correction increased what you owe. A CP12 means your refund amount changed, sometimes for the better. A CP13 means the correction wiped out both a balance and a refund. Each notice has a section labeled “What we changed on your return” that walks through the specific adjustments.3Internal Revenue Service. Understanding Your CP11 Notice
If you agree, pay any balance by the date on the notice and update your personal copy of the return. If you disagree, contact the IRS by that same date. The IRS will reverse most changes if you respond in time. Miss the deadline and you lose the right to have the changes reversed and your right to appeal to the U.S. Tax Court, though the IRS will still consider late supporting documents.
Your Income Doesn’t Match What Was Reported
The IRS receives copies of every W-2, 1099, and 1098 issued in your name. An automated system called the Automated Underreporter function compares those third-party reports against what you put on your return. When the numbers don’t match, a tax examiner reviews the discrepancy and the IRS sends a CP2000 notice proposing an adjustment to your income, credits, or deductions.4Internal Revenue Service. Topic No. 652, Notice of Underreported Income – CP2000
A CP2000 is not a bill. It’s a proposal. The notice lays out what you reported, what the payer reported, the payer’s name and ID number, and the proposed changes to your tax. It also includes a response form.
If the CP2000 is correct and you have nothing else to add, sign the response form and pay the proposed balance. If it’s correct but you also have unreported deductions or credits, file an amended return (Form 1040-X) with “CP2000” written at the top and send it in with your response form. If you disagree, respond by the deadline with documentation showing the IRS data is wrong, such as a corrected 1099 or proof you reported the income on a different line. Ignoring a CP2000 doesn’t make it go away; the IRS will eventually send a formal bill.5Internal Revenue Service. Understanding Your CP2000 Series Notice
The IRS Needs a Missing Document
Sometimes the IRS can’t finish processing a return because something is missing. You might get a letter asking for a Form W-2 that wasn’t attached, a Schedule K-1 from a partnership or trust, or documentation for a particular deduction or credit. These letters aren’t accusations. They’re the IRS asking for one more thing before it can move forward.6Internal Revenue Service. 3.0.101 Schedule K-1 Processing
Gather the specific documents the letter asks for and send them back by the deadline. You can respond by mail, or for many notice types you can upload documents through the IRS Document Upload Tool. You’ll need either the access code printed on your letter or the notice number to use it.7Internal Revenue Service. IRS Document Upload Tool
The IRS Needs to Verify Your Identity
The IRS flags returns that look suspicious. Perhaps the return was filed from an unusual location, claimed a refund routed to a different bank account than in prior years, or matched patterns associated with identity theft. When that happens, the IRS sends a letter (commonly Letter 5071C or Letter 4883C) asking you to verify your identity before processing the return.8Internal Revenue Service. Understanding Your Letter 4883C
Follow the instructions in the letter to verify online or by calling the Taxpayer Protection Program Hotline. Have the letter, a copy of the return in question, and a prior-year return in front of you. If you did file the return, the IRS continues processing it. If you didn’t file it, say so immediately; the IRS will remove the fraudulent return from your records, and you can then file your actual return on paper.9Internal Revenue Service. IRS Identity Theft Victim Assistance: How It Works
One important boundary: do not file Form 14039 (Identity Theft Affidavit) if you got one of these letters. The verification process in the letter replaces that form.9Internal Revenue Service. IRS Identity Theft Victim Assistance: How It Works
You Have a Balance Due
If you filed a return but didn’t pay the full amount owed, the IRS sends a CP14 notice. It’s the first balance due notice, showing how much you owe and when to pay. Paying immediately stops additional interest and penalties from piling up.10Internal Revenue Service. Understanding Your CP14 Notice
Two separate penalties often stack on unpaid tax. The failure-to-file penalty runs 5% of unpaid tax for each month or partial month a return is late, capped at 25%. The failure-to-pay penalty is 0.5% per month, also capped at 25%. When both apply in the same month, the failure-to-file penalty drops to 4.5% so the combined rate stays at 5%.11Internal Revenue Service. Collection Procedural Questions Interest also accrues on unpaid tax from the original due date until you pay in full.12Internal Revenue Service. Topic No. 653, IRS Notices and Bills, Penalties and Interest Charges
If you file more than 60 days late, the minimum failure-to-file penalty is the lesser of the full tax owed or a fixed dollar amount the IRS adjusts annually.13Office of the Law Revision Counsel. 26 U.S. Code 6651 – Failure to File Tax Return or to Pay Tax
Ask About First-Time Penalty Abatement
If you filed on time and had no significant penalties for the three tax years before the penalty year, you may qualify for first-time penalty abatement. This is an administrative waiver the IRS grants on request; you don’t have to prove reasonable cause. It can wipe out the failure-to-file or failure-to-pay penalty for a single tax period, which can be worth hundreds or thousands of dollars. Call the number on your notice or write to the IRS to request it.14Internal Revenue Service. 15Taxpayer Advocate Service. What to Do If You Receive Notification Your Tax Return Is Being Examined or Audited The IRS always opens audits by mail, never by phone.16Internal Revenue Service. IRS Audits
Most audits are correspondence audits, handled entirely by mail: the IRS asks about specific line items and you mail back supporting documents. These tend to be narrow. Office audits require you to visit an IRS office with records. Field audits are broader, with an agent reviewing your financial records at your home or business, sometimes across multiple tax years.
You have the right to have someone represent you at any stage, including appeals. Attorneys, CPAs, and enrolled agents can represent you fully; a family member or your return preparer may represent you in more limited circumstances. Form 2848 (Power of Attorney) authorizes a representative. Representation matters most during office and field audits, where the scope of questioning is broader.
Collection Letters After an Unpaid Balance
If you don’t pay after the initial CP14, the IRS escalates through a series of collection letters, each carrying more weight than the last. The final notice before enforcement is typically a CP504, the formal Notice of Intent to Levy. It warns that the IRS can seize funds from your bank accounts, garnish wages, and take your state tax refund to satisfy the debt.17Internal Revenue Service. Understanding Your CP504 Notice
The IRS can also file a federal tax lien, a legal claim against your property that alerts creditors the government has a stake in what you own. A lien doesn’t seize anything, but it can damage credit and complicate selling property. A levy actually takes property: money from bank accounts, a portion of wages, even Social Security benefits.18Taxpayer Advocate Service. Notice of Intent to Levy
The collection process moves slowly enough that you have time to act, but only if you don’t ignore the letters. If you can’t pay in full, the IRS offers structured options including short-term payment plans, monthly installment agreements, offers in compromise, and currently not collectible status.19Internal Revenue Service. Payment Plans; Installment Agreements
How to Tell If the Letter Is a Scam
IRS impersonation scams are common, and the anxiety of getting an IRS letter is exactly what scammers exploit. A few rules cut through the noise. The IRS makes first contact by mail, not by phone, email, text, or social media. If someone calls claiming to be the IRS and demands immediate payment by gift card, prepaid debit card, or wire transfer, that’s a scam. The real IRS will not threaten immediate arrest or demand payment without giving you the chance to question the amount.20Internal Revenue Service. Ways to Tell If the IRS Is Reaching Out or If It’s a Scammer
To confirm a paper letter is real, log in to your IRS Online Account. Legitimate notices appear there. You can also search the notice number on the IRS website or call 800-829-1040.2Internal Revenue Service. Online Account for Individuals
What to Do With Any IRS Letter
Whatever the reason for the letter, the same habits apply. Open it as soon as it arrives and find the notice number in the upper right corner. Read the whole letter. Note the response deadline. Don’t panic; most IRS letters have a clear ask and a clear timeline.1Internal Revenue Service. Understanding Your IRS Notice or Letter
Respond by the deadline even if your response isn’t complete. A partial response that shows good faith beats silence. For many notices you can upload documents through the IRS Document Upload Tool rather than mailing paper. Look for an access code on your letter or pick the notice number from the tool’s dropdown.7Internal Revenue Service. IRS Document Upload Tool
Keep a copy of every letter you receive and every response you send. If the situation is complex, the amounts are significant, or you’re unsure what the IRS is asking, get help from a tax professional before responding. If you can’t afford professional help and the IRS hasn’t resolved your issue within 30 days, or you’re facing financial hardship because of the delay, the Taxpayer Advocate Service offers free, confidential assistance to both individuals and businesses.21Internal Revenue Service. Who May Use the Taxpayer Advocate Service