Responding to Math Error Notices

The following page is for informational and educational purposes only. It is not legal advice and it does not create an attorney-client relationship with our clinic. If you need help please Contact Us.

How do I know if I’ve received a Math Error Notice?

If you receive a letter from the IRS, look to the box in the top right-hand corner.

  • Look at what is listed next to “Notice” at the top of the box.

  • You have received a Math Error Notice if you see CP 11, CP 12, or CP 13.

What is a Math Error Notice?

A Math Error Notice lets you know that the IRS disagrees with something you reported on your tax return and has changed it. The IRS either believes you made a mistake in your calculations, or they otherwise think a correction needs to be made to your return.

Here is what each type of Math Error Notice means:

CP 11

The IRS has made a change to your tax return and believes you owe money.

CP 12

The IRS has made a change regarding your refund. They believe you made an overpayment. You do not owe money.

CP 13

The IRS believes there was a miscalculation on your tax return. However, they do not think you owe money, nor do they think you should receive a tax refund.

What do I do if I’ve received a Math Error Notice?

Make sure you read the entirety of your Math Error Notice. The “header” in the top right-hand corner will let you know what type of notice, your taxpayer identification number, and a phone number to contact the IRS.

The next section summarizes why the IRS has adjusted your return and what they think you should owe.

Next, there will be details on how to respond.

In the next section, the IRS will explain the changes they’ve made with calculations and the lines of your return used in making them.

If you agree with the assessment made by the IRS in your:

CP 11

You should pay the tax you owe. You can make online payments or apply for a payment plan if you are unable to pay in full here.

CP 12

You do not need to respond. If you are due for a refund, you should receive it within 4 to 6 weeks.

CP 13

You do not need to respond.

If you disagree with any type of Math Error Notice, you have two options: You may respond by mail or phone call. Please note that regardless, you must respond within 60 days of receiving your Math Error Notice. If you do not respond within 60 days the IRS will move forward with collections if they believe you owe money. Making a phone call will likely save you time, as it will take 30-60 days to hear back from the IRS via mail.

  1. Call the number listed on the header at the top of your notice.

  2. Send a letter describing what you disagree with and why. Be sure to include a copy of your Math Error Notice. The contact information is at the bottom of the first page of your notice.

Please Note: the IRS will initiate correspondence with you by mail. If you receive something claiming to be a Math Error Notice by email or telephone, you should not engage with it, as it is fraudulent.