IRS CP23 - Estimated Tax Mismatch: What To Do Now

A CP23 notifies you that the IRS found a discrepancy between the estimated tax payments you claimed on your return and the actual payments credited to your account. This can result in a balance due if the IRS's records show fewer payments than you claimed.

The clock: this notice generally carries a 30 days response window. Rights and options expire with it — the date on the letter controls, not the day you found it.

Do this, in order

1. Compare your records with IRS records
2. Gather proof of estimated payments
3. Contact us to help resolve the mismatch
4. Provide canceled checks or bank statements
5. Respond within 30 days

Straight answers

What causes an estimated tax credit calculation mismatch?

Common causes include: failing to trace extension payments, recording a payment in the wrong tax year, omitting joint-filing payment details, or the IRS misapplying a payment to the wrong taxpayer (especially with common names).

How do I prove I made an estimated tax payment the IRS says they didn't receive?

Pull your bank records showing the check or electronic payment, the date it cleared, and the amount. If you paid electronically, download the confirmation from IRS.gov/payments or EFTPS. Send copies with your response.

Where this sits in the machine

This notice belongs to the examination stage of the IRS process. Understanding the stage matters more than the single letter — read IRS Examination: The Mechanics of Defense for the map, and the letter-by-letter anatomy in the firm's notice decoder for CP23.

What representation changes

Representation means the examiner talks to your representative, not to you. With a signed Form 2848, an Enrolled Agent receives the information document requests, controls what goes back, and keeps the examination inside its stated scope.