CP23· Math-error correction
CP23 — Estimated-tax payment discrepancy
- Category
- Math error
- Urgency
- Date on notice
- Response window
- see notice
- Key form
- Form 1040-X
Respond by the date printed on your individual notice.
Why the IRS sent this
Discrepancy between estimated tax payments claimed on the return and IRS records of payments received.
Response window
The IRS detail page for CP23 does not state a fixed day count. The response-by date is printed on your individual notice — read the date at the top-right corner.
What to do
Required action
Verify your estimated-payment records, pay the balance by the date on the notice, or contact the IRS if disputing the adjustment.
Key form: Form 1040-X — verify the current revision on irs.gov/forms-pubs before filing.
Appeal path
Informal — call the IRS
Informal — call the IRS at the number on the notice. Often resolved by locating an estimated payment credited to the wrong year or wrong taxpayer.
Notes from the primary source
Estimated-tax-credit reconciliation is processed under the IRC §6213(g) math-error procedures. The §6213(b) 60-day abatement-request window may apply but is NOT restated on the detail page — verify against the statute directly before relying.
Calm-corrective
Only the IRS can resolve your notice
We are not a CPA firm, not a law firm, not an Enrolled Agent firm, and not affiliated with the IRS. We don't accept payments on your behalf, settle your debt, or call the IRS for you. What we do: explain what your notice means, point you to the right IRS form, cite the statute that authorizes the action, and surface the appeal path. Then you call the number on the notice, file the form, or hire a licensed professional.
Related notices
Likely next or sibling codes
Source
Verified against the official IRS detail page on irs.gov/individuals/understanding-your-cp23-notice. Always re-verify against the IRS page before acting.