IRS CP23 Notice (2026): Return Changed — What Was Adjusted & How to Respond

Received an IRS CP23 Notice? This notice means the IRS changed your tax return after processing it — most commonly because the estimated tax payments you reported didn’t match what the IRS has on record.

If you ignore it, interest and penalties can continue to grow. If you respond correctly, most CP23 issues are fixable.

What Is an IRS CP23 Notice?

An IRS CP23 Notice is issued when the IRS adjusts your return after processing. In most cases, the IRS believes your estimated tax payments were reported incorrectly or don’t match their records.

In plain English: “Your numbers didn’t match ours, so we corrected your return and recalculated your balance.”

Why Did the IRS Change Your Return?

• Estimated tax payments were overstated or understated
• Payments were applied to the wrong tax year
• The IRS never received one or more payments you claimed
• A payment was credited to another account or taxpayer

What Was Adjusted on Your Return?

Look for the section titled “What We Changed on Your Return.” This section shows exactly how the IRS recalculated your taxes.

• The estimated tax payments the IRS credited
• The difference between your reported payments and IRS records
• Your updated balance due
• Any added penalties or interest

How to Respond to an IRS CP23 Notice

Step 1: Review the Numbers

Compare the notice with your own records:

• Quarterly estimated tax payments
• Bank confirmations or EFTPS receipts
• Your filed Form 1040

Step 2: If You Agree With the IRS

• Pay the balance by the deadline on the notice
• Use IRS Direct Pay, EFTPS, or mail payment with the voucher
• Keep a corrected copy of your return for your records

Step 3: If You Disagree With the IRS

• Respond within 60 days using the contact info on the notice
• Include proof such as canceled checks or bank statements
• Send copies only — never original documents

What Happens If You Ignore a CP23 Notice?

Interest and penalties continue to accrue until the issue is resolved. Ignoring the notice can lead to additional IRS letters and possible collection actions.

How to Avoid CP23 Notices in the Future

• Verify estimated payments in your IRS Online Account before filing
• Use IRS Direct Pay or EFTPS for clear records
• Double-check estimated payment totals on your return
• Save confirmation numbers for every payment

Final Takeaway

An IRS CP23 Notice is serious — but usually manageable. Review it promptly, compare your records, and respond before the deadline to avoid unnecessary penalties.

Sources

• Internal Revenue Service — Understanding Your CP23 Notice
• Taxpayer Advocate Service — IRS Notice CP23 Overview
• IRS — Estimated Tax Payments & Online Account