IRS CP11 Notice: Math Error — Balance Due
A CP11 notice means the IRS corrected what it considers a miscalculation on your return and the change results in a balance due — you have 60 days to dispute it before the assessment becomes final.
Deadline calculator
The CP11 clock runs from the date printed on the notice — not the day you opened it.
Estimate only, based on the standard 60-day CP11 window. Your notice controls — always use the specific date printed on it.
What a CP11 actually means
"Math error" is broader than arithmetic: mismatched credits (Child Tax Credit, stimulus/recovery amounts), wrong SSNs for dependents, and income transcription errors all trigger CP11s.
The 60-day window matters: request abatement within it and the IRS must reverse the change and follow normal deficiency procedures (with full appeal rights) if you disagree. Miss it, and you owe the tax unless you pay and claim a refund later.
What to do, step by step
- 1Compare the notice's 'changes to your return' section against your filed copy line by line.
- 2If the IRS is right, pay or set up a payment plan — interest runs from the return due date.
- 3If you disagree, call or write within 60 days and request abatement of the math-error assessment.
- 4Provide documentation supporting your original figures (credit eligibility, dependent SSNs, etc.).
Common questions
Why does my CP11 say my Child Tax Credit was wrong?+
Credit-eligibility mismatches (age, SSN validity, income phase-outs) are the most common CP11 trigger. If your records show the credit was right, dispute within 60 days — after that, reversal requires a refund claim.
Received a CP11? Get it handled.
Talk to a tax specialist about your notice — free, no pressure, no judgment.