CP11 Notice: IRS Fixed a Math Error and You Owe Tax

A CP11 notice means the IRS found what it believes is a miscalculation or similar error on your tax return, corrected it, and now shows that you owe tax. This is a "math error" notice. No examiner has audited your return; the correction came from processing. These notices are common and often simple to resolve, either by paying or by asking the IRS to undo the change.

Why you got a CP11

The IRS can fix certain errors on its own without an audit. The law calls these mathematical or clerical errors. Common examples:

• Arithmetic mistakes, such as adding or subtracting wrong.
• Numbers carried over wrongly from one line or schedule to another.
• A credit claimed without the required information, such as a missing or mismatched Social Security number for a child.
• A credit or deduction above a legal limit, or a dependent who is over an age limit, such as claiming the Child Tax Credit for a child who turned 17.
• Payments or withholding that do not match IRS records.

When the correction leaves you with a balance due, you get a CP11. If it changes a refund instead, you would get a CP12.

What the CP11 says

Look for:

• "What we changed on your return": a short explanation of each change.
• The amount you owe, including any penalty and interest so far.
• The date to pay, and a separate date by which to contact the IRS if you disagree.
• "Where to find more information": the toll-free number to call.
• A payment stub and mailing address.

The IRS's internal guidance says the law gives you 60 days from the date of a math error notice to ask that the change be reversed (the tax code calls this a request for abatement). Your notice shows the exact date.

What to do

If you agree

Pay the amount owed by the date on the notice to avoid more penalties and interest. You can pay online, by phone or by mail; your IRS Online Account also shows your balance and payments. If you cannot pay in full, set up a payment plan. If you can't pay because of circumstances beyond your control, the IRS says to contact it by the due date, as you may qualify for penalty relief.

If you disagree

Call the toll-free number in the "Where to find more information" section before the date shown. The IRS says the phone is the fastest way to resolve many of these errors, and you can often fax a missing form while on the call.

The IRS says it will reverse most changes that increased what you owe if you ask in time. You do not have to give a reason or send documents, although doing so may speed things up. If the IRS does not get information supporting your original return, it may send the case to audit. In that case, audit staff should contact you within 6 weeks to explain the process and your rights.

If you need to make another correction

If you find a different mistake on the return, file Form 1040-X. Our amended return guide explains how.

What happens if you ignore it

If you don't pay or contact the IRS, the balance grows with interest and the late payment penalty. You will get reminder notices such as the CP501 and CP503, and eventually a CP504 notice of intent to levy. If you don't contact the IRS by the date on the CP11, you lose the formal right to have the change reversed and to appeal it to the U.S. Tax Court. The IRS says it will still consider documents you send later and may reverse the change if it agrees.

Is this notice real?

The IRS generally contacts people first by mail, and CP11 is a standard notice. To confirm, check your IRS Online Account for the balance, or call the IRS using a number from irs.gov. The IRS does not demand payment by gift card, prepaid debit card or wire transfer. Learn more about IRS scams.

IRSV.com is an independent guide and is not affiliated with the IRS. This page is general information, not tax or legal advice. Rules change; confirm details on IRS.gov or with a tax professional. Found an error? Tell us.