IRS underreporter notice
A CP2000 is a letter from the IRS saying the income or payments on your tax return do not match what employers, banks and other third parties reported. It proposes changes to your return and shows what you might owe if the changes stand.
The IRS says to respond to a CP2000 usually within 30 days of the date printed on the notice. The exact date is on your letter. If you cannot make it, call the toll-free number on the notice and ask for more time.
Sign and return the response form. Then pay the amount shown, or ask about a payment plan if you cannot pay in full. Interest builds on any unpaid balance, so replying early helps.
Write a short explanation and attach proof. Common reasons are income that was already reported on your return, a form that was wrong or belongs to someone else, or investment sales where your cost basis was higher than what was reported. Say which items you dispute and point to the document that supports you.
The IRS says it will send another notice, a Statutory Notice of Deficiency (CP3219A). That notice explains your right to challenge the decision in Tax Court, and it carries its own deadline. Do not let that notice sit unopened.
This guide is general information, not tax or legal advice. Your notice is the final word on your dates and amounts. If you are unsure, see when to get professional help.