IRS Notice CP45: What It Means & What to Do
CP45 means the IRS could not apply your overpayment to next year's estimated taxes as you asked. Learn how to adjust your estimated payments to avoid underpaying.
Written and maintained by Joseph Lancaster, Settlement Officer since January 2013
Published · Checked against IRS sources on
Quick answer
What is an IRS CP45 notice and what should I do?
CP45 means the IRS could not apply your overpayment to next year's estimated taxes as requested. Read why, update your records and raise your current-year estimated payments with Form 1040-ES so you do not underpay.
Who this applies to: Taxpayers who asked to apply an overpayment to the next year's estimated tax.
What can change this answer
- The notice is your confirmation
- Recalculate with Form 1040-ES
- Underpaying can bring a penalty
You asked the IRS to apply an overpayment to next year's estimated taxes, and it could not apply all or part of it. The notice explains why.
Immediate Steps to Take
- 1Read the notice to see why the overpayment was not applied
- 2Update your own copy of your tax return
- 3Increase your current-year estimated payments so you do not underpay
What CP45 means
An overpayment is tax you paid during the year, through withholding or estimated payments, beyond what you owed. You can have it refunded or applied to next year. CP45 tells you the amount you expected to carry forward was not applied, so your estimated payments may now fall short. The IRS will not send a separate confirmation; this notice is the confirmation.
Adjusting your estimated payments
Use Form 1040-ES to recalculate your estimated payments, and Publication 505 for more guidance. If a balance remains, explore your payment options.
Frequently Asked Questions
How do I find out what changed on my return?
Call the IRS at the number on your notice. It can explain what happened with your return.
Will the IRS send another notice confirming the overpayment?
No. The IRS says CP45 is the confirmation of how your overpayment was applied.
Authority Citations
This content is based on the following official IRS sources. All links open in a new tab.
Information current as of 2026. Tax laws change frequently. Verify with official IRS sources before taking action.
Important information