IRS Notice CP11: What It Means
The IRS page “Understanding your CP11 notice”, last reviewed August 11, 2026, says: “We corrected one or more mistakes on your tax return. As a result, the amount you owe has changed.”
When we checked on November 2, 2026, the IRS page showed “Page Last Reviewed or Updated: 11-Aug-2026”. The IRS wording in quotation marks abouta CP11 notice comes from that IRS page.
Maintained by Archie Chang · Reviewed November 2, 2026 · Methodology & sources
What the IRS page says the notice is about
“We corrected one or more mistakes on your tax return. As a result, the amount you owe has changed.”
Response timing, as the IRS words it
IRS line before it: “If you agree with the changes we made”
“[…] Pay the amount owed by the date shown on your notice to avoid additional penalties and interest. […]”
IRS line before it: “If you disagree with the changes we made”
“[…] Contact us at the number shown on the notice by the date indicated.”
Steps the IRS page lists
“Read your notice carefully to see what was changed on your return and how those changes affected the amount you owe.
If you agree with the changes we made
Pay the amount owed by the date shown on your notice to avoid additional penalties and interest.
Make arrangements to pay over time if you can't pay the full amount right now.
Correct the copy of your tax return that you kept for your records, but do not send it to us.
If you disagree with the changes we made
Contact us at the number shown on the notice by the date indicated.”
Frequently asked questions
How does the IRS page say to find out what changed on a CP11 return?
The IRS page for CP11, last reviewed August 11, 2026, answers its question “How can I find out what caused my tax return to change?” this way: “Review the “What we changed on your return” section of your notice. For more information about the errors on your return, call us at the number shown in the “Where to find more information”.”
What does the IRS say about disagreeing with the changes in a CP11?
The IRS page for CP11, last reviewed August 11, 2026, answers its question “What should I do if I disagree with the changes you made?” this way: “If you disagree, contact us by the date shown on your notice. Call us at the toll-free number shown in the “Where to find more information” section of your notice. The fastest way to resolve many return errors is by telephone. Some cases require additional information that you may provide verbally. If we need a missing or corrected form or document, you can fax your documents using either a fax machine or online fax service while on the telephone. Protect yourself when sending digital data by understanding the fax service’s privacy and security policies. We’ll reverse most changes we made if we increased the amount you owe or if your return requested a refund. You don’t need to provide an explanation or additional documents when you request the reversal, but doing so may help us resolve your case more quickly. If we don’t receive information that supports your original return, we may forward your case for audit, in which case the audit staff will contact you within 6 weeks to explain the process and your rights. If you don’t contact us by the date shown on your notice, you will lose formal rights to have the change(s) reversed, as well as your right to appeal our decision to the U.S. Tax Court. However, if you contact us and send supporting documentation after that date, we will still consider that information and we may reverse the change(s) to your return if we agree with you.”
What does the IRS say about interest on a CP11 balance?
The IRS page for CP11, last reviewed August 11, 2026, answers its question “Will I be charged interest on the money I owe?” this way: “To avoid interest charges, full pay the amount owed by the due date shown on your notice. If you don't pay in full by that date, interest will accrue on the unpaid balance from the date the return was due.”
What does the IRS say about a penalty on a CP11 balance?
The IRS page for CP11, last reviewed August 11, 2026, answers its question “Will I receive a penalty if I can't pay the full amount?” this way: “Yes, you will receive a late payment penalty. You can contact us at the number shown on your notice if you can't pay the full amount shown in your specific notice because of circumstances beyond your control. Contact us by the due date of your notice and depending on your situation, we may be able to remove the penalty. See our Penalty relief page for what information to have available.”
Related FedRateCalc pages
- Amended tax return (Form 1040-X) (how an amended return is filed)
- IRS payment plan calculator (estimates of installment payments)
- IRS penalty abatement (how penalty relief requests are described)
- IRS tax transcript (how to get a transcript of a return)
Other IRS notice pages
Sources (checked November 2, 2026): IRS: Understanding your CP11 notice (page last reviewed August 11, 2026)