Updated October 19, 2026. Quick answer: A CP13 means the IRS corrected one or more mistakes on your return and, after the changes, you are not due a refund and do not owe an additional amount: your account balance is zero. If you agree, you do not need to respond. If you disagree, contact the IRS at the number on the notice by the date shown.
Quick reference
| Item | As the IRS describes it |
|---|---|
| What it is | A return correction that leaves a zero balance |
| If you agree | No response needed |
| If you disagree | Contact the IRS by the date on the notice |
| To make another correction | File Form 1040-X |
| Audit follow-up | Audit staff contact within 6 weeks if support is not received |
| Time to allow for an IRS reply (Tax Topic 651) | At least 30 days |
| Audit staff contact if support is not received | Within 6 weeks (42 days) |
| Amend later: generally within (Form 1040-X instructions) | 3 years of filing the original return, or 2 years of paying the tax, whichever is later |
What the notice says
“We corrected one or more mistakes on your tax return. You’re not due a refund nor do you owe an additional amount because of our changes. Your account balance is zero.”
What you need to do
The IRS says “If you agree with the changes we made, you don’t need to respond to your notice.” It suggests you “Correct the copy of your tax return for your records, but do not send it to us.”
To see the changes, read the notice section titled “What we changed on your return” and call the number in “Where to find more information” if you want detail.
If you disagree
“If you disagree, contact us by the date shown on your notice.” The fastest route is by phone, and “We’ll reverse most changes we made if we increased the amount you owe or if your return requested a refund.” Providing an explanation is optional.
The IRS warns that after the date you “will lose formal rights to have the change(s) reversed, as well as your right to appeal our decision to the U.S. Tax Court.” If you do not send support that backs up your return, “we may forward your case for audit”.
If you need another correction
The IRS says “You’ll need to file a Form 1040-X, Amended U.S. Individual Income Tax Return” to make a correction See Form 1040-X and its line pages for how.
If you need to correct the return yourself later
The Form 1040-X instructions give the time limit: “Generally, for a credit or refund, you must file Form 1040-X within 3 years (including extensions) after the date you filed your original return or within 2 years after the date you paid the tax, whichever is later.” See Form 1040-X for the form itself.
Where this comes from
The IRS page read for this page is the one titled Understanding your CP13 notice on irs.gov, as served on 2026-10-19. Your own notice controls: the dates, amounts and phone or fax numbers on it are the ones to use, and the IRS can update its page after we read it.
For IRS notices in general, Tax Topic 651 says “You should allow at least 30 days for a reply from the IRS.” It also says “Keep a copy of all IRS correspondence for your tax records.”
Common mistakes
- Filing Form 1040-X to answer a CP13. The IRS says a 1040-X is for a new correction, not a reply to the notice.
- Waiting past the date on the notice if you disagree.
- Sending your corrected copy of the return. It is for your own records.
- Treating a zero balance as a sign nothing changed. The change can still alter the figures on your copy.
Related: the IRS math error notice, IRS Notice CP12, IRS Notice CP11, and IRS notices and letters.
Sources
- IRS, Understanding your CP13 notice (irs.gov): https://www.irs.gov/individuals/understanding-your-cp13-notice
- Instructions for Form 1040-X (Rev. December 2025), Amended U.S. Individual Income Tax Return: https://www.irs.gov/pub/irs-pdf/i1040x.pdf
- IRS, Tax Topic 651, Notices: what to do (irs.gov): https://www.irs.gov/taxtopics/tc651
Read from the IRS pages linked above on October 19, 2026. General information, not tax or legal advice. Your own notice and facts decide the outcome, and the number printed on your notice is the right place to confirm anything consequential.