Why the IRS Sends a CP12 Notice
The IRS sends a CP12 when its corrections change the refund you expected. That includes cases where you expected to owe or to have an even balance, and the correction left you getting a refund instead.
To see what changed, read the “What we changed on your return” section of your notice. If you need more detail, call the number listed under “Where to find more information.”
Make sure you have the right notice, too. A CP12 is about possible mistakes the IRS found on your return. A CP2000 notice is about income reported by third parties that doesn’t match your return.
How to Respond to IRS Notice CP12
Once you’ve read the changes, your next step depends on whether you agree with them.
| If you agree | If you disagree | |
|---|---|---|
| What to do | Nothing. No response is required. | Call the toll-free number on your notice. |
| Deadline | None | The date shown on your notice |
| Documents needed | None | Not required, but they may speed things up |
| What happens next | Your refund check should arrive in 4–6 weeks, unless you owe other tax or debts. | The IRS will reverse most changes that reduced your requested refund. |
If You Agree With the Changes
You can update your own copy of the return to match the IRS’s figures, but don’t send it to the IRS. If a tax preparer did your return, ask them to correct their copy too.
Your check could still be smaller than the notice shows if you owe other money. This is called a refund offset. It means the IRS can apply your refund to other federal tax you owe or to certain debts it’s required to collect.
If You Disagree With the Changes
Call the IRS at the toll-free number on your notice before the date it lists. The IRS says contacting them by phone is the fastest way to resolve many errors, and you can fax documents during the call if asked.
You don’t need to explain or send documents to request a reversal. Still, if you don’t provide supporting information, the IRS may forward your case for audit. In that case, audit staff will contact you within 6 weeks.
If You Miss the Deadline
If you miss the date on your notice, you lose two rights. These are the formal right to have the change reversed and the right to appeal to the U.S. Tax Court. Even so, the IRS will still consider documentation you send later and may reverse the change if it agrees with you.
What CP12G and CP12U Notices Mean
You might get a CP12G or CP12U instead. According to the IRS guide, they also mean the IRS corrected a miscalculation and you’re due a refund. If you disagree with one of these, contact the IRS within 60 days of the notice date.
When You Might Need an Amended Return
If you find an error on your return that the CP12 didn’t address, you can correct it with an amended return on Form 1040-X.
Sources
- IRS, Understanding Your CP12 Notice (last reviewed Aug. 11, 2026)
- IRS, Understanding Your CP12G or CP12U Notice
- IRS, About Form 1040-X, Amended U.S. Individual Income Tax Return
