How to read a math error notice
When the IRS changes a Form 945 or 1042 because the arithmetic or a line does not agree with its records, it sends a CP 102 (a balance due on Form 941, 943, 944 or 945) or, for Form 1042, a CP 107 (balance due), CP 117 (overpayment) or CP 127 (a zero or under-$1 balance). Each change on the notice carries a two-digit math error code, and the explanation printed next to it is fixed text from Document 6209. The code tells you which line the IRS changed and so what to check. For a deposit mismatch (code 26 for an annual return, 24 for a quarterly one), compare your EFTPS records with the deposits on the account transcript before you reply; the transaction code decoder reads the transcript.
The notices a payer receives
From Document 6209's notice lists, the ones that concern backup withholding, Forms 945 and 1042, and the W-2 reconciliation. The explanation column is the IRS's own wording.
| Notice | IRS description |
|---|---|
| CP 2100 | Check Your Backup Withholding List ("Large" payers) |
| CP 2100A | Please Check Your Backup Withholding List ("Small" payers) |
| CP 543 | Backup withholding notification- Payer notification to begin backup withholding on taxpayer(s) listed |
| CP 544 | Backup withholding notification to payer to stop backup withholding |
| CP 545 | Backup withholding notification to payer to discontinue backup withholding |
| CP 546 | Backup withholding notification- Special backup withholding list |
| CP 102 | Math error on Form 941, 943, 944 or 945 resulting in a net balance due. |
| CP 107 | Math error on Form 1042 resulting in a net balance due. |
| CP 117 | Math Error on Form 1042 resulting in a net overpayment. |
| CP 127 | Math error on Form 1042 with the net result a zero or less than a $1.00 balance. |
| CP 137B | Annual Notification of FTD Deposit Requirements (Form 945) |
| CP 136 | Annual Notification of FTD Deposit Requirements (941, 941SS) |
| CP 230 | Notification that an adjustment has been made under CAWR Reconciliation Program. Issued after the CAWR case has been closed and a tax adjustment has been made, balance due, even balance or refund due. |
| CP 240 | DP Adjustment – (CAWR) Balance Due of $5 or more and module not in TDA/BAL DUE status. TC 290 (BS 550-559) posts to MFT 01, 04, 11 modules. |
| CP 251 | NOTICE OF Employment Tax Problem—Why You’re Tax May Be Changed. Notice issued to taxpayer under the Combined Annual Wage Reporting (CAWR) program to advise of a wage discrepancy (potential overpayment or underpayment). 253 Request for W-2 not filed with Social Security Administration- Notice issued to taxpayer under the Combined Annual Wage Reporting (CAWR) program to advise of missing forms W-2 .The notice is generated from the CAP system, not BMF. |
| CP 267 | Issued to notify taxpayer of excess credits in a tax module in which no math error return posted and a request taxpayer response for resolution of the condition. |
| CP 268 | Issued to notify taxpayer of excess credits in a tax module in which a math error returned posted and a request for resolution of the condition. |
| CP 215 | Notification of a Civil Penalty assessment. |
| CP 259 | First Notice for Nonfiler Return Delinquency is issued to inform the taxpayer that we have no record of a tax return filed. |
| CP 504B/604B | Final Notice –Balance Due – BMF, no response allows for lien filing and levies on certain assets |
CP 2100 and CP 2100A are filed under the information returns program; CP 543 to CP 546 are the C-notice series sent when the IRS itself orders backup withholding on a payee who underreported interest or dividends (C-notices).
Math error codes for Forms 945, 941, 943 and 944
One table covers the whole employment and nonpayroll withholding family (Forms 941, 941-SS, 943, 944, 944-SS and 945). Codes that refer to Social Security, Medicare, tips or the advance earned income credit cannot apply to a Form 945, which reports only withheld income tax. Two COVID-era deferral codes (40 and 41) are left out because the public edition prints them in a damaged layout.
| Code | What the notice says |
|---|---|
| 01 | We found an error in the computation of the balance due or the overpayment amount. |
| 02 | We cannot allow the amount (or a portion of the amount) shown as an adjustment because it was not claimed within 3 years from the time the original return was filed, or within 2 years from the time the tax was paid. |
| 03 | We found an error in the computation of your total taxes. |
| 04 | The corrections on Form 941C weren’t shown as adjustments on your return. |
| 05 | We found an error in the computation of corrections on your Form 941C. |
| 06 | The excess withheld income tax must be claimed for a tax period ending within the same calendar year for which it was originally reported. An adjustment to income tax withheld for a prior year can only be allowed if the adjustment is the result of an administrative error. There was no indication on your return that the adjustment was the result of an administrative error. Please see Publication 15/15A or the form instructions for information on administrative errors. |
| 07 | We found an error in the computation of your total Social Security/Medicare tax. |
| 08 | Non-profit organization became liable for Social Security and/or Medicare taxes effective on 01-01-1984. Since we found no check mark entry in the box on the return or other indication that the wages were not subject to Social Security and/or Medicare taxes, we have computed the taxes and adjusted your return accordingly. |
| 09 | We found an error in the adjustment amount for "Current quarter's fractions and cents". |
| 10 | We found an error in the adjustment amount for "Current quarter's sick pay". |
| 11 | We found an error in the adjustment amount for "Tips and Group Term Life Insurance". |
| 12 | We found an error in the adjustment amount for the "Current Year’s Income Tax Withholding". |
| 13 | We found an error in the adjustment amount for "Prior quarter's Social Security and Medicare taxes”. |
| 14 | We found an error in the adjustment amount for “Special Additions for Federal Income Tax”. |
| 15 | We found an error in the adjustment amount for “Special Additions for Social Security and Medicare tax”. |
| 16 | We found an error in the computation for "Total Adjustments". |
| 17 | We found the amount paid with your return was erroneously shown on the Advance Earned Income Credit Line. |
| 18 | The Advance Earned Income Credit payment cannot be the same as or more than the Social Security/Medicare Taxes. |
| 19 | We found an error in the subtraction of your Advance Earned income Credit payments from your total taxes. |
| 20 | The total Federal Tax Deposit amount was erroneously shown on the Advance Earned Income Credit line. |
| 21 | We found an incorrect social security tax rate was used to compute your social security taxes. |
| 22 | We found an incorrect Medicare tax rate was used to compute your Medicare taxes. |
| 23 | The Advance Earned Income credit (AEIC) payment cannot be more than the appropriate percentage of the total wages and other compensation you paid. For 1995 and subsequent years, the appropriate percentage is 20.4%. |
| 24 | We found the amount reported as total Federal Tax Deposits for the quarter differs from the amount we have credited to your account. |
| 26 | We found the amount reported as total Federal Tax Deposits for the year differs from the amount we have credited to your account. |
| 27 | We adjusted your tax as shown because we did not receive a reply to our request for additional information. |
| 28 | We found an error in the adjustment amount for “Prior Year’s income tax adjustments”. |
| 29 | We found an error in the adjustment amount for “Prior Year’s income tax adjustments”. |
| 30 | We found an error in the adjustment amount for “Prior year’s Social Security and Medicare tax adjustments”. |
| 31 | We are processing your request to adjust previously reported Federal Income Withholding tax, or taxes on Social security Wages and/or Tips or Medicare Wages and will send you another notice within 45 days. In the future, you should submit such adjustment requests on the appropriate Adjusted Employment Tax return. |
| 32 | We are not processing your request to adjust previously reported Federal Income Withholding tax, or taxes on Social security Wages and/or Tips or Medicare Wages. Beginning with tax year 2009, you should submit such adjustment requests on the appropriate Adjusted Employment Tax Return. We have processed the remainder of your return. |
| 33 | We found an error in the addition of the “Total deposits for this year” and the “COBRA Premium Assistance Payments”. |
| 34 | We did not process your request for a credit for the employer’s share of the Social Security tax (6.2%) on the exempt wages of qualified employees. The number of qualified employees and the amount of their exempt wages must be provided on the return. We have processed the remainder of your return. Request the credit by submitting the appropriate Adjusted Employment Tax return. |
| 35 | We did not process your request for a credit for the employer’s share of the Social Security tax (6.2%) on the exempt wages of qualified employees. The total of the “Taxable social security wages” and “Taxable social security tips” lines must be greater than or equal to the amount shown on the “Exempt wages/tips paid to qualified employees” line. We have processed the remainder of your return. Request the credit by submitting the appropriate Adjusted Employment Tax return. |
| 90 | Fill-In Narrative. Note - This Math Error contains fill-in free form text with maximum of 10 lines, 70 characters per line. |
| 91 | You are liable for Social Security and Medicare Tax under a Section 218 Agreement (for state or local governmental agencies) with the Social Security Administration |
| 93 | We found the amount of Federal Tax Deposits for the quarter differs from the amount we have credited to your account. |
| 94 | We have disallowed your negative entry reported on Line 12a. If you need to adjust your COBRA credits claimed from a previous period, you must file |
Math error codes for Form 1042
| Code | What the notice says |
|---|---|
| 01 | The balance due, or the amount you overpaid, was not correct. |
| 02 | An error was made when the total tax you owe for the year was figured. |
| 26 | The amount reported as total Federal Tax Deposits for the year was not correct. |
| 90 | Fill-in narrative. Note — This Math Error contains fill-in free form text with maximum of 10 lines, 70 characters per line. |
The public edition lists four codes for Form 1042. A code 26 means the deposits shown on the return differ from what the IRS credited; if a deposit went to the wrong form or period, see deposits on the wrong form or year.
Questions people ask
Where does this list come from?
IRS Document 6209, the IRS's internal reference to its codes, published with official-use-only lines removed at irs.gov/downloads/irs-6209. This tool uses Section 9 of the 2023 edition: the information returns, business and IDRS notice lists, and the business math error codes.
My notice number is not found. Why?
Individual (IMF) notices and most letters (Letter 98C, 854C and similar) are in other parts of Document 6209 or are letters rather than CP notices. The site's notice pages cover the ones payers receive most.
What is code 02 on a Form 941 or 945 notice?
An adjustment that came too late: “We cannot allow the amount (or a portion of the amount) shown as an adjustment because it was not claimed within 3 years from the time the original return was filed, or within 2 years from the time the tax was paid.”
What is code 06?
Prior-year income tax withholding cannot be adjusted on the current return unless the adjustment fixes an administrative error, and the return did not say it did. Corrections of withholding for an earlier year go on Form 945-X (Form 945-X).