IRS / Tax Error Code
IRS / Tax Status & Refund Codes
IRS Notice Classification
CP12 notice | Math error correction notice
Industry
IRS / Tax
Canonical
/irs-tax/error-codes/cp12-notice/
Last Updated
Feb 25, 2026
Summary
This notice indicates that the IRS corrected a mathematical or clerical error on the return.
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What This Code Means
A CP12 notice reflects that the IRS made an adjustment due to a mathematical or calculation error identified during processing. It indicates that the original figures were modified to correct discrepancies. The notice explains the adjustment and its impact on refund or balance. It does not represent an audit or fraud determination. The transcript may show related adjustment codes reflecting the correction.
Where Users Usually See This Code
- In mailed IRS correspondence
- On account transcripts with adjustment codes
- During refund recalculation
Why This Code Appears
- Calculation error on return
- Mismatch in reported amounts
- Clerical correction required
- System-detected arithmetic discrepancy
What Typically Happens Next
- Refund amount may change
- Account balance may adjust
- Adjustment codes may post
What This Code Is Not
- It is not a freeze
- It is not an audit notice
- It does not automatically indicate penalty
Troubleshooting Checklist
- □ Review transcript adjustment entries
- □ Confirm updated refund or balance amount
- □ Compare correction with original filing
- □ Consult official IRS resources if clarification is needed
Notes And Edge Cases
The notice details the correction made. Transcript entries reflect numerical adjustments corresponding to the correction. Reviewing updated balance clarifies impact.
Related Codes
8 links
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