IRS CP23 Notice: Estimated Payment Mismatch — Balance Due
A CP23 notice means the estimated tax payments the IRS has on record don't match what you claimed on your return, so your refund changed or you now owe — usually because a payment was misdated, misapplied, or claimed twice.
Deadline calculator
The CP23 clock runs from the date printed on the notice — not the day you opened it.
Estimate only, based on the standard 21-day CP23 window. Your notice controls — always use the specific date printed on it.
What a CP23 actually means
Self-employed filers see these most. Common causes: a January estimated payment claimed in the wrong year, a payment applied to a spouse's account after a name/SSN mixup, or simple typos in the payments claimed.
If the IRS record is wrong, proof of payment fixes it. If your return overstated payments, the balance is real but the penalties are often abatable.
How to recognize a real CP23
An IRS campus sends it when the payments claimed on the return don't match IRS records. That includes estimated tax payments, credits carried over from another year, and payments sent with an extension. The corrected return shows a balance due.
- The heading reads 'Changes to your [year] Form 1040' with 'Amount due:'. The text says the return was changed 'to match our record of your estimated tax payments, credits applied from another tax year, and payments received with an extension to file'.
- A section titled 'Payments credited to your account for [year]' lists what the IRS actually has on record, or states that no estimated payments were found.
- A 'Your payments and credits' table shows the IRS figures for withholding, estimated payments, other credits, and other payments.
- Like other math-error notices, it explains the 60-day written reversal right. It also includes a detachable payment stub and a due date.
What to do, step by step
- 1Compare the IRS's payment list against your bank records and IRS online account.
- 2If a payment is missing from their list, respond with proof (confirmation numbers, bank statements).
- 3If you actually overclaimed, pay the difference or set up a plan, and ask about penalty abatement.
- 4Fix the source going forward — schedule estimated payments through your IRS online account so they're always applied correctly.
Illustrative example
Example: Priya's fourth-quarter payment landed in the wrong year
Priya (an illustrative freelancer) claimed $8,000 in 2025 estimated tax payments. Her CP23 dated March 23, 2026 showed only $6,000 in the 'Payments credited to your account' section and an amount due of $2,063, including penalty and interest.
She checked her bank statement and IRS online account and found the problem. Her $2,000 January 2026 payment, meant for the fourth quarter of 2025, had been entered in IRS Direct Pay as a 2026 payment. The money wasn't missing. It was credited to the wrong year.
She called the number on the notice with her Direct Pay confirmation number and asked the IRS to move the payment to 2025, and followed up in writing within 60 days. Once the payment was moved, the balance and the related penalty dropped off.
Names and numbers are made up to show how this notice typically plays out.
Mistakes that make a CP23 worse
- Claiming estimated payments when you didn't make any. The IRS says the most common cause of a CP23 is an incorrect entry on the estimated tax line, especially by people who don't usually pay estimated tax.
- Claiming a prior-year overpayment credit without checking whether that year was later changed or offset. The 'credits applied from another tax year' figure has to match what the IRS actually carried over.
- Sending a check to cover the gap when the payment was really just misapplied to another year or a spouse's account. Paying twice creates a credit you then have to recover.
- Asking the IRS to waive the interest. The IRS says interest on a CP23 can't be waived. Late-payment penalties do adjust automatically if the IRS corrects its own payment-record error.
What happens if you ignore a CP23
The IRS assumes you agree, and penalties and interest keep adding up from the due date shown. After 60 days you lose the right to have the change reversed without paying first. Unpaid amounts then follow the regular balance-due reminder path.
Can come next
Common questions
The IRS says I made fewer estimated payments than I did — what do I do?+
Respond with payment proof: IRS confirmation numbers, EFTPS records, or bank statements. Payments applied to the wrong year or spouse's account are the usual culprits and get corrected on documentation.
Checked against IRS primary sources — see how we source these guides. You can verify any notice directly at IRS.gov. The dates and instructions printed on your specific notice always control. Official IRS explanation: Understanding your CP23 notice.
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