CP2000: Notice of Proposed Changes (Underreporter Inquiry)

What it is

A proposal, not a bill and not an audit. The IRS matched the income on your return against what employers, banks, brokers, and other payers reported on forms like W-2 and 1099; a tax examiner then reviewed the discrepancy, and the IRS is proposing changes to your tax.

Why you got it

Sent by the Automated Underreporter (AUR) program when third-party income documents don't match the amounts on your filed return.

The deadline structure

The notice prints a specific 'respond by' date — typically 30 days from the notice date (60 days if you live outside the U.S.). The date printed on YOUR notice controls.

Always use the response date printed on the notice itself, not a typical window.

The options printed on it

1. Agree with all proposed changes — sign and return the response form (both spouses if filed jointly)
2. Partially agree — explain which items you dispute and include documentation
3. Disagree entirely — explain why with supporting documents (corrected 1099, cost-basis records, etc.)

How to respond

• The response form attached to the notice (mail or fax to the address/number printed on it)
• Many CP2000s can be answered online via the IRS Documentation Upload Tool if the notice lists an access code
• Phone number printed in the top corner of the notice for questions

What ignoring it leads to

If you don't respond by the printed date — or the IRS can't resolve the discrepancy from what you send — it generally issues a CP3219A Statutory Notice of Deficiency. That notice starts your Tax Court petition window: 90 days from the mailing date, or 150 days if it is addressed to you outside the United States (IRC §6213(a)). During that window the proposed tax generally can't be assessed unless you agree.

Next letter if nothing changes: CP3219A (Statutory Notice of Deficiency)

Mistakes people make with a CP2000

• Treating it as a final bill and paying without checking the matched items — the proposal can be wrong (duplicated 1099s, missing cost basis on stock sales are common)
• Filing a stand-alone amended return instead of responding through the CP2000 process — for the items the notice proposes, the IRS makes the correction itself, so a separate 1040-X isn't needed. But if the CP2000 is right AND you have OTHER income, credits, or expenses to report, IRS Topic 652 says to complete Form 1040-X, write 'CP2000' on top, and send it WITH your CP2000 response by the due date
• Missing that the response form asks both spouses to sign on a joint return

Official sources

• Understanding your CP2000 notice
• Topic no. 652, Notice of underreported income – CP2000
• Understanding your CP3219A notice (Statutory Notice of Deficiency)
• 26 U.S.C. § 6212 — Notice of deficiency
• 26 U.S.C. § 6213 — Petition to Tax Court (90/150-day rule; assessment restriction)

Our summary paraphrases these sources. Last verified: AI-RESEARCH 2026-06-27 (Codex/gpt-5.5) + cross-ref 2026-07-02 (2nd frontier model; §6213/§6212 + CP3219A re-fetched live) — matched-and-reviewed wording, added 150-day outside-US window, nuanced 1040-X guidance; human re-verify before launch; scamCheck added 2026-07-11 (verified 5071c/4883c anti-impersonation language reused). Your printed notice always controls.

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