CP45 Notice: The IRS Did Not Apply Your Overpayment to Next Year’s Tax as You Asked
By Forrest Baumhover, CFP®, EA · Last verified October 28, 2026
A CP45 tells you the IRS moved less of your overpayment to next year’s estimated tax than you asked, or none of it. Your estimated tax payments for the year may now fall short.
If you got this letter
Got a CP45 in the Mail?
On your tax return, you asked the IRS to keep some or all of your extra tax payment and count it toward next year’s tax. The CP45 says the IRS could not apply that amount the way you asked.
The notice explains why. Read it, fix your own copy of the return, and raise your estimated tax payments for this year so you do not pay too little.
The IRS page says it will not send another notice to confirm the change. This notice is the confirmation, so keep it with your tax records.
What the CP45 notice says
The IRS page puts it in one line: “We couldn’t apply your overpayment to your next year’s estimated taxes like you asked.” An overpayment, the page explains, means you paid more tax than you owed during the year, through paycheck withholding or estimated payments. You can choose to get that extra amount back as a refund or apply it to next year’s taxes.
The Internal Revenue Manual (IRM), the IRS’s staff rulebook, calls that choice a credit elect. It says the IRS sends a CP45 when only part of the amount you asked for, or none of it, went to next year and no other notice about the return explains the change.
Why the IRS moved less than you asked
Your notice states the reason, so start there. The law points to the most common one: other debts come first. IRC 6402(a) lets the IRS apply an overpayment to any federal tax you owe. IRC 6402(c) says the IRS takes past-due child support out of an overpayment before it credits any of it to a future tax year.
The IRM sets the same order for the other debts the Treasury Offset Program collects, such as debts to other federal agencies and past-due state income tax. It says the IRS reduces the credit elect by the debt you owe, still credits any amount above the debt the way you asked, and sends a CP45 to tell you about the reduction “and the possible need to make additional estimated tax payments.”
A change to your return can also shrink the overpayment. The IRM says a math error that reduces the credit elect comes with a different notice, the CP10. If you do not know what changed, the IRS page tells you to call the number on your notice.
What you need to do
The IRS page lists three steps. Read the notice carefully. Update your own copy of your tax return. Adjust this year’s estimated tax payments “so you don’t end up underpaying.”
To refigure the payments, the IRS page points to Form 1040-ES, Estimated Tax for Individuals, and Publication 505, Tax Withholding and Estimated Tax. Plan to cover the amount the CP45 says did not carry over.
Married couples have one more path. The IRM calls a spouse an “injured spouse” when a joint overpayment went to a debt that spouse does not owe, and that spouse files Form 8379, Injured Spouse Allocation, to ask for their share. When that allocation frees the credit and the tax year has not ended, the IRM says the IRS applies it to the year automatically. If that fits you, ask the IRS about Form 8379 at the number on your notice.
If you owe a balance after the change, the IRS page points to your payment options. Our can-I-pay-over-time check shows whether a payment plan or another option fits. To see the account itself, the IRS page points to your Online Account. If you have an account transcript, our transcript analyzer explains each line in plain words.
Why the gap matters this year
This is the part people miss. The CP45 changes the math for the year already under way. If you planned this year’s estimated payments around a credit that never arrived, you have paid less so far than you think.
The IRS page lists Form 2210, Underpayment of Estimated Tax by Individuals, Estates and Trusts, among its helpful forms, next to the advice to adjust your payments. The notice is your signal to close the gap with your next payments.
What the CP45 does not mean
It does not mean the IRS lost your money. The IRS page says this notice “is your confirmation of how we applied your overpayment to your account.” Your notice shows where the money went.
The IRS page lists no reply among its steps, but it says your notice “may include next steps,” so read it for any. The other steps are to fix your records and adjust your payments.
What people mistake the CP45 for
Some readers file the CP45 away and keep making the estimated payments they planned. That is the costly mistake: those payments now fall short by the amount that did not carry over.
Others read it as a sign of an error on the return. The law puts other debts ahead of next year’s credit, so a CP45 can follow a return with no error at all.
Common Questions
Why did the IRS not apply my overpayment?
Your notice gives the reason. The law lets the IRS apply an overpayment to federal tax you owe, and to debts such as past-due child support, before it credits the rest to next year.
Do I need to reply to a CP45?
The IRS page does not ask for a reply. It asks you to read the notice, update your copy of the return, and adjust your estimated tax payments.
Will the IRS send another notice once it applies the money?
No. The IRS page says this notice is your confirmation of how the IRS applied your overpayment.
How do I figure my new estimated payments?
The IRS page points to Form 1040-ES, Estimated Tax for Individuals, and to Publication 505 for more guidance.
How do I find out what changed on my return?
Call the number on your notice. The IRS page says the IRS can explain exactly what happened with your return.