The CP11 is a math-error notice. The IRS reviewed your return, found what it considers a miscalculation or inconsistency, corrected it, and the change resulted in a balance due. "Math error" is broader than arithmetic — it includes mismatched credits, missing forms, dependent or Social Security number problems, and similar issues the IRS can fix without a full audit. You have the right to agree or dispute the change.
What this notice means
A CP11 tells you the IRS changed your return and that you now owe money as a result. The notice should explain what was changed and why. While the IRS is often right, math-error adjustments are sometimes mistaken — a credit you correctly claimed may have been disallowed, or a form the IRS thought was missing was actually filed.
Why you received it
- A credit (such as a child tax credit or recovery rebate) was claimed in an amount the IRS adjusted.
- Income, payments, or withholding figures did not match IRS records.
- A dependent or Social Security number issue affected a credit.
- An arithmetic or transcription error changed your tax.
Deadlines and what happens if you ignore it
| Your options | What to do |
|---|---|
| You agree | Pay the balance or set up a payment plan |
| You disagree | Contact the IRS within 60 days to dispute the change |
| You miss 60 days | You lose the right to reverse it without a formal audit/refund claim |
| You ignore it | The balance is assessed and collection notices follow |
The 60-day window matters
You generally have 60 days to dispute a math-error adjustment and have the IRS reverse it without going through audit reconsideration or filing a formal claim. Miss it and correcting the change gets much harder. See IRS Topic 651 — Notices.
How to respond to a CP11
- Read what changed. Compare the IRS adjustment to your original return.
- Decide if it is correct. If the IRS is right, plan to pay; if not, gather documentation.
- Dispute within 60 days if you disagree, in writing with supporting records.
- **Set up a payment plan** if you agree but cannot pay in full.
- **Request penalty abatement** on any penalties added to the new balance.
How USCTS helps
We compare the CP11 adjustment against your filed return and the IRS’s records to determine whether the change is correct. If the IRS made an error, we dispute it within the 60-day window to reverse the balance. If the adjustment stands and you owe, we arrange an affordable installment agreement or, where appropriate, an Offer in Compromise, and we pursue penalty abatement on the added charges.
Think your CP11 is wrong? Let us check it.
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