CP2000 Notice Response: How to Answer an IRS Underreporter Letter

A CP2000 notice response is the most common reason U.S. taxpayers deal with the IRS outside an audit. The notice says the income or payment information the IRS received from employers, banks and brokers does not match what you reported, and it proposes a change to your tax. It is not a bill, but ignoring it can lead to one. If you have wages, brokerage sales, stock compensation or retirement distributions in more than one account, or you moved between countries during the year, mismatches are common and usually fixable with the right paper.

What is a CP2000 notice, and why did I get one?

The IRS runs an automated underreporter (AUR) program. It compares the W-2, 1099 and similar forms that payers file with the income, credits and deductions on your return. When a potential discrepancy survives a tax examiner's review, the IRS issues a CP2000. The notice lists what you reported, what the payer reported, the payer's name and the forms concerned, and the proposed changes. It includes a response form, an envelope and a list of payment methods.

Typical triggers for readers of this site include a brokerage Form 1099-B that shows no cost basis for shares sold, a Form 1099-R for a distribution you rolled over or reported elsewhere, interest or dividends on an account opened during a year of arrival, and Form 1042-S or 1099 income reported under the wrong taxpayer identification number. Sometimes the payer is simply wrong. The IRS tells taxpayers in that case to ask the payer for a corrected form or a statement explaining the error.

CP2000 notice response: step by step

1. Read the whole notice. Note the tax year, the date on the notice, the response date and each item the IRS says is underreported.
2. Pull your records. Get your filed return, the information forms for the year, brokerage statements, and a transcript of your original return if you need one.
3. Match each item. For every line on the notice, find where it sits on your return. Often the income is there under a different line or an amended amount.
4. Choose agree, disagree or amend. The table below sets out the three paths.
5. Complete and sign the response form. If you filed jointly, both spouses sign. If you want someone else to speak to the IRS, complete the authorization section of the form or file a power of attorney.
6. Reply in a trackable way. Use the IRS document upload tool (JPG, PNG or PDF), the fax number for the office printed on the notice, or the mailing address in the top left corner. Keep proof.
7. Pay or arrange to pay what you accept. Interest accrues until the balance is paid. See IRS payment plans and offers.

If the same error affects another year, the IRS advises filing an amended return for that year too, which can stop further penalties from building.

What is the deadline, and what if I miss it?

The response date is printed on your notice. The IRS says to respond within 30 days of the notice date, or 60 days if you live outside the United States, for a quick resolution. It also explains that interest in a CP2000 is generally calculated from the original due date of the return to 30 days after the notice date, and that paying the proposed amount within 30 days stops additional interest and possibly additional penalties from accruing.

If the IRS does not hear from you, or cannot resolve the discrepancy, it may send another notice and a bill, and it states that it will send a statutory notice of deficiency. That notice, such as a CP3219A, is not a bill or an audit; it proposes a change and starts the Tax Court clock. The IRS says it will work with you during the 90-day period, but that work does not extend the time you have to petition. Publication 556 gives 90 days from the date of the notice, or 150 days if the notice is addressed to you outside the United States; the notice itself shows the final day. The Tax Court cannot consider a petition filed late.

Penalties and interest to expect

For 2025 returns, as in IRS guidance published in 2026, an accuracy-related penalty is 20 percent of the portion of the underpayment attributable to negligence or disregard of the rules, or to a substantial understatement. For individuals, a substantial understatement exists if you understate tax by the greater of 10 percent of the tax required to be shown on the return or $5,000. The IRS warns that a CP2000 may carry penalties that are not yet shown on the notice. Interest is charged on penalties, and you can ask for relief through the penalty abatement playbook if you acted with reasonable cause and in good faith.

How other countries compare

A worked example

Dev, an H-1B engineer living in Naperville, sold 400 company shares in 2025. His broker's Form 1099-B shows $40,000 of proceeds and no basis. Because the vesting income was already in his W-2, he reported a basis of $38,000 on Form 8949 and a $2,000 gain. The CP2000 treats the full $40,000 as gain and proposes tax on $38,000 of extra income. At an assumed 24 percent rate that is $9,120, plus a 20 percent penalty of $1,824 and interest. Dev's reply includes the signed response form, the broker's year-end statement, the vesting record and the W-2 showing the income, and a one-page explanation. All figures are hypothetical. If the IRS accepts the documents, the proposed change drops to zero.

Mistakes to avoid

• Paying immediately without checking. If you do not owe it, you give up money and may waive a position.
• Sending only an explanation. The IRS wants support, so attach statements, W-2s and basis records.
• Missing that one spouse must sign a joint response.
• Treating a notice of deficiency like a CP2000. After a notice of deficiency the Tax Court deadline is fixed.
• Forgetting other years with the same pattern.

How we can help

We review CP2000 notices for clients across Aurora, Naperville and the Fox Valley, reconcile them to your return and records, prepare the response and, with a signed power of attorney, deal with the IRS for you. If foreign income or accounts are part of the story, we coordinate with your Canadian CPA or Indian Chartered Accountant so the filings agree. We do not guarantee a result. See IRS and state tax representation, our 1040 roadmap and the first steps guide. Browse the notices hub for every guide in this series.

Frequently asked questions

General information only. It is not tax, legal, accounting or immigration advice for your situation, and rules change; confirm the current rules with the official source or a licensed professional in the relevant country.