The IRS Says Your Numbers Don't Match Theirs.
They're Frequently Wrong. You Have 60 Days to Prove It.

The CP2000 is the IRS's computer matching program at work. Every year the IRS receives millions of 1099s, W-2s, K-1s, and other third-party income reports. Their system compares those against your filed return. When the numbers don't align, you get a CP2000 — a formal proposed adjustment to your tax liability.

The IRS is often wrong. Third-party reports contain errors. Income you already reported may appear under a different form or line. Deductions you were entitled to may not have been captured. The proposed amount is frequently higher than what you actually owe — and in some cases you owe nothing at all.

You have 60 days to respond. Agree with the proposal and pay. Or dispute it — in writing, with documentation. Most people agree without checking because the letter looks authoritative and the process seems intimidating. That's a costly mistake. The right response is always a careful review first.

The CP2000 proposes an additional tax assessment — not just a balance on existing taxes, but a new liability created by income the IRS believes you underreported. The proposed amount includes the additional tax owed, an Accuracy-Related Penalty of 20% of the proposed underpayment, and interest from the original due date of the return in question.

The Accuracy-Related Penalty is the critical charge here. It's not a collection penalty like Failure-to-Pay — it's a penalty for the underpayment itself, and it's assessed the moment the CP2000 becomes final. If the IRS proposes $8,000 in additional tax, you're looking at a $1,600 penalty before interest is added. Interest on CP2000 assessments accrues from the original April 15 due date of the return — often 12–18 months before you even received the notice.

If the underpayment is determined to be due to fraud (rare, but possible in egregious cases), the penalty increases to 75%. If it's due to negligence, the 20% accuracy penalty stands. In either case, the penalties can be contested if you have a documented reasonable basis for your original filing position.

The CP2000 is generated entirely by the IRS's Automated Underreporter (AUR) unit — a computerized matching system, not a human auditor. The AUR receives electronic copies of every 1099-NEC, 1099-INT, 1099-DIV, W-2, K-1, and other information return filed by payers. It matches those against your return line by line. When the totals don't match, it generates a CP2000 automatically.

This matters because the AUR system is not infallible. It matches gross amounts — it does not know about offsetting expenses, basis adjustments on asset sales, reinvested dividends, or income already reported elsewhere on the return under a different line. A 1099-B showing $50,000 in stock proceeds might correspond to a $47,000 cost basis and a $3,000 gain — but the AUR flags the full $50,000 as unreported income unless your Schedule D showed it clearly.

The CP2000 is a proposed assessment. You have 60 days to agree, partially agree, or dispute it. If you dispute, the case goes to the AUR unit for manual review — an actual IRS employee looks at your documentation. If they sustain the full amount, you receive a Notice of Deficiency (CP3219A), which opens the door to Tax Court. Most CP2000 cases are resolved at the AUR level with the right documentation.