What CP2000 actually is
CP2000 comes from the IRS Automated Underreporter (AUR) program. A computer compared the W-2s, 1099s, and other third-party information returns it received about you to your filed return, found a discrepancy, and produced a proposed adjustment. The notice tells you the proposed change to tax, interest, and sometimes penalties — and gives you a date by which to respond.
Critical framing: CP2000 is a proposal, not an assessment. The IRS has not yet decided you owe the additional tax. They are asking you to review their math and tell them whether they got it right.
Step 1 — Check the IRS's math against your records
Start with the back of the CP2000. The IRS lists every income item they think you missed, paired with the third-party reporter (e.g., "1099-NEC, $4,800, ABC Consulting"). For each item:
- Find the matching record in your own files (the 1099 form, the bank statement, the broker tax document).
- Confirm whether you reported it. If yes, where? Sometimes a 1099-NEC for $4,800 is on Schedule C, but the IRS's matching system didn't see it because it was rolled into a larger Schedule C number.
- If the income wasn't reported, decide whether the IRS's third-party data is correct. Sometimes 1099s are issued in error — wrong taxpayer, wrong year, wrong amount.
Step 2 — Decide your response: agree, disagree, or partial
Agree (the IRS is right)
Sign the response form, return it by the date on the notice, and either pay the balance or set up a payment plan using the IRS's Online Payment Agreement or Form 9465. Once you sign, the IRS converts the proposal into an assessment. Tax, interest, and any computed penalties are then due under normal collection procedures.
Disagree (the IRS is wrong)
Sign the part of the response form indicating disagreement, attach a written explanation, and include the documents that support your position — the 1099 you actually received, your Schedule C with the income clearly reported, the corrected information return from the issuer, etc. Mail or fax it back by the date on the notice.
If you originally reported correctly, often the AUR unit will agree with you when they see your documentation and close the case. If the AUR unit disagrees with your disagreement, your case escalates to a statutory notice of deficiency — CP3219A — which gives you a 90-day window to petition the U.S. Tax Court under IRC §6213(a). The 90-day Tax Court window cannot be extended.
Partial agreement
The IRS's math is sometimes right on some items and wrong on others. Sign the partial-agreement section of the response form, attach documentation for the items you dispute, and the AUR unit will recompute. This is more common than people expect — the AUR matching system is bulk and rule-based, so partial errors are normal.
When to hire a pro
For straightforward CP2000 cases — you forgot to report a single 1099, the math is small, the documentation is clear — you can usually handle the response yourself. The IRS's response form is designed to be fillable without a professional.
Hire a credentialed professional (CPA, Enrolled Agent, or tax attorney) when:
- The proposed deficiency is large and you don't agree with the IRS's position
- The facts are complex (foreign income, S-corp basis, partnership K-1s, virtual currency, real-estate dispositions)
- You're receiving multiple CP2000s for multiple years
- The case has already escalated to CP3219A and a Tax Court petition is in your decision tree
- A penalty is asserted and you want to argue reasonable cause
The right professional is one who can read the proposal, your return, and the third-party documents together — and tell you which items to fight, which to concede, and what penalty abatement arguments are realistic. The IRS's Directory of Federal Tax Return Preparers is a verifiable starting point.
If you missed the response window
If you didn't respond and CP2000 has already escalated to a CP3219A statutory notice of deficiency, your timeline shifts. You now have 90 days from the CP3219A date to either resolve the matter informally with the IRS or file a Tax Court petition. See our page on CP3219A — the 90-day letter for the next step.