CP11: Math Error, Balance Due
The IRS found a calculation error on your return that results in you owing more tax.
Deadline
60 days to dispute; pay as soon as possible to limit interest
Do I owe money?
Yes
What does CP11 mean?
CP11 means the IRS corrected a math or clerical error on your return that increased your tax liability. Common causes include incorrectly calculated credits (such as the Earned Income Tax Credit or Child Tax Credit), mismatched figures between lines on the return, or transcription errors. The IRS has already made the change and is informing you. You have 60 days to dispute if you believe the correction was wrong.
What should you do next?
- 1Review the notice to see exactly what the IRS changed and why
- 2Compare your original return to the IRS's corrected figures
- 3If you agree: pay the balance shown (with interest) by the due date
- 4If you disagree: call the number on the notice within 60 days with your documentation — do not just ignore it
Frequently asked questions
Can the IRS just change my return without asking me?
Yes — for math and clerical errors only. The IRS has authority to correct obvious calculation mistakes without sending a formal deficiency notice. CP11 is their way of telling you they've done this. If you disagree with the correction, you can dispute it within 60 days.
Is CP11 the same as an audit?
No. A math error correction is not an audit. The IRS did not examine your deductions or income — they only corrected a calculation error they identified.
What if the math error on CP11 was actually my tax software's fault?
That doesn't change your liability — you are still responsible for errors in your return. However, if the software caused you to overpay fees or penalties, some tax software companies offer audit defense or error reimbursement programs.
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Explain my noticeLast updated: 2026-05-18