Notice Type
An IRS CP23 notice means the estimated tax payments or other payments reported on your tax return do not match the payments the IRS posted to your account. The IRS changed the return to match its records, and the adjustment created or increased a balance due. The notice may also include other processing changes.
IMPORTANT: Compare every estimated payment and any prior-year credit shown on CP23 with your own records before paying or disputing the balance. If you agree with the IRS changes, pay the amount due by the date printed on the notice. If you disagree, contact the IRS by the date shown and have proof of the payments or credits available.
Before You Respond
Start with a payment-by-payment reconciliation. Compare the CP23 with your Form 1040 estimated-tax line, IRS Online Account, prior-year overpayment applied forward, bank records, EFTPS confirmations, cancelled checks, and any payment vouchers or transcripts. Confirm that each payment was made under the correct taxpayer identification number, tax year, and payment type. A single misapplied or omitted payment can materially change the balance.
Know Before You Act
CP23 does not necessarily mean the taxpayer failed to pay estimated tax. The mismatch can result from an incorrect entry on the return, a payment applied to the wrong year or account, a prior-year credit that differs from the return, or another processing change. If the IRS correctly adjusted the account, the remaining balance may be valid. If a payment is missing or misapplied, the account may need correction before the balance is accepted. A CP24 estimated-payment credit notice addresses the companion situation in which an adjustment may create a credit or refund; a CP14 balance-due notice can provide related account information.
Start with a secure notice upload and a free IRS notice summary so you can identify the tax year, payments the IRS credited, the amount claimed on the return, the balance due, and the response date. The optional $45 Review & Guidance may help reconcile the notice against payment records, identify missing or misapplied payments, and prepare an Action Plan. Think Twice Tax does not contact the IRS or trace payments directly with the IRS as part of the standard service.