IRS CP11: Changes to Your Tax Return — Balance Due (Math Error)

The IRS corrected a math error on your return and now says you owe money.

Your deadline

60 days to dispute the changes; 21 days to pay if you agree

If you believe the IRS's math correction is wrong, you must dispute it within 60 days. After 60 days, the adjusted balance becomes final and penalty-and-interest accrual cannot be reversed.

How soon to act: High priority

What this notice means

CP11 means the IRS found a math or calculation error on your tax return and corrected it — resulting in a balance due. This is different from CP14, which confirms a balance you calculated yourself. With CP11, the IRS changed your numbers.

Common causes include errors in calculating credits (Child Tax Credit, EITC), incorrect deduction amounts, computation errors on schedules, or incorrectly entered Social Security income. The IRS corrects these automatically during processing without opening a formal audit.

You have the right to dispute the IRS's correction if you believe the original return was correct. Disagreements with math error adjustments must be submitted within 60 days, after which the adjusted balance becomes final.

How it works

1
Compare the IRS's corrections to your original return line by line
2
If the correction is right, pay the balance or set up a payment plan
3
If the correction is wrong, dispute it in writing within 60 days with your supporting calculations

Other options

A tax professional can quickly evaluate whether the IRS's correction is accurate

If you do nothing

Treat the adjusted balance as final after 60 days if unchallenged
Add failure-to-pay penalties and interest from the original due date
Send collection notices (CP501, CP503, CP504) if the balance is not paid

Which sounds like you?

Installment Agreement

If you agree with the balance, set up a payment plan

Penalty Abatement

Remove failure-to-pay penalties if they apply

Audit Defense

Professional dispute of an incorrect math error adjustment

Common questions

How do I dispute the CP11 correction?

Write to the IRS at the address on the notice, explain the error in the IRS's correction, and include your calculations and supporting documentation. A tax professional can draft this response for you.

What if the IRS made the wrong math correction?

The IRS is not infallible. Math error corrections are sometimes themselves wrong. If your original return was correct, you have 60 days to assert that position. After 60 days, the adjusted amount is treated as correct.