Can an IRS notice be wrong, and how do I dispute one I disagree with?

Yes — IRS notices, especially automated ones like the CP2000, are frequently incomplete or mistaken because they rely on matching data without context. If you disagree, respond in writing by the stated deadline, check the 'I do not agree' box on the response form, and attach a clear explanation plus supporting documents. Keep a copy and send it with tracking. If the IRS still disagrees, you can request a conference with the IRS Independent Office of Appeals, and if you receive a formal Notice of Deficiency you have 90 days to petition the U.S. Tax Court without first paying the tax. For smaller amounts, Tax Court has a simplified small-case procedure. Missing deadlines is the biggest risk, so calendar every date the moment a notice arrives.