CP23 Notice: The IRS Changed Your Estimated Tax Payments — What to Do

What a CP23 Notice Means

The IRS sends CP23 when it finds a difference between the amount of estimated tax payments on your return and the amount it posted to your account. It corrects your return, and if the correction leaves a balance, you get this notice.

The IRS CP23 page (updated November 3, 2026) says the most common cause is an incorrect entry on the estimated tax line of the return.

A CP23 is not an audit. It is a correction based on the payments the IRS has on record. This guide is current as of November 11, 2026.

Why the Numbers May Not Match

The estimated tax line on Form 1040 includes the quarterly payments you made for the year and any overpayment from the year before that you chose to apply. A typing error, or counting a payment that was made for a different year, is enough to trigger a CP23.

Sometimes the payment was made but posted differently from what your return shows, for example to another tax year. If the IRS later fixes a misapplied payment, it says the penalty and interest adjust automatically.

Read the notice carefully. It lists the payments the IRS found, and comparing that list with your own is the quickest way to spot the difference.

How to Check Your Payments

Sign in to your IRS online account and look at the payment history for the tax year. It shows each payment the IRS has on record and the year it was applied to.

Compare it with your own records: bank statements, payment confirmations and last year's return if you applied an overpayment. For each payment, note the date, the amount and the tax year you meant it for.

If every payment on your list is on the IRS's list, the IRS is probably right and your return had the wrong figure. If a payment is missing or posted to another year, you have something to show the IRS.

If You Agree: Pay or Set Up a Plan

The IRS says to pay the amount owed by the date on the notice to avoid more penalties and interest. You can pay online at IRS.gov with Direct Pay from your bank account, or by debit or credit card (the card processor charges a fee).

If you cannot pay in full, apply for a payment plan. Our free payment options calculator helps you compare the choices, and the IRS payment plans page lists the current fees.

Pay what you can now, even if you need a plan for the rest. Interest is charged on the unpaid balance every day.

If You Disagree: Call by the Date on the Notice

The IRS says to contact it at the number shown on the notice by the date shown. Have the notice, your return and your proof of each payment ready before you call.

Ask the IRS to find any payment that is missing or posted to another year and move it to the right one. Write down the date of the call, the name or ID number of the person you spoke with and what they said.

Penalties, Interest and Relief

The IRS says you will usually get a late-payment penalty. This is the failure-to-pay penalty under IRC 6651(a)(2): 0.5% of the unpaid tax for each month or part of a month, up to 25%.

Interest is different. The IRS says it cannot reduce interest for reasonable cause or first-time relief, because the law requires it until the account is fully paid.

For the late-payment penalty, you have options. For a tax year 2025 return, first check your IRS account for automatic penalty relief (AEP). If it was not applied and your 3-year history is clean, use our FTA eligibility checker to see whether you can ask for First-Time Abatement. Reasonable cause is another path.

If your real payments were lower than you thought, an estimated tax penalty under IRC 6654 may also apply. First-Time Abatement and AEP do not cover it. Our free estimated tax calculator shows how it is worked out.

Avoiding a CP23 Next Year

Keep a simple list of every estimated payment you make: the date, the amount, the tax year and the confirmation number.

Before you file, compare that list with the payment history in your IRS online account, and enter on your return only the payments that were made for that year.

Our estimated tax penalty guide explains the quarterly due dates and the safe harbor rules.