A CP2000 is the IRS’s “underreporter” notice: its computers matched the income reported on your return against W-2s, 1099s, and other forms, found a mismatch, and proposes changes (more tax, sometimes a refund). It is not a bill and not an audit — it’s a proposal you can agree with or dispute.
Deadline: respond by the date on the notice — usually 30 days (60 if you’re outside the U.S.). If you don’t, the IRS issues a Notice of Deficiency (CP3219A), which starts a strict 90-day Tax Court clock.
Work the notice
Compare the IRS’s figures to your records, line by line. Common causes: a 1099 you forgot, a brokerage’s gross proceeds without your cost basis, or income that’s actually reported elsewhere on your return.
- You agree — sign the response form, check “I agree,” and pay or set up a plan.
- You partly/fully disagree — check “I do not agree,” and send a signed explanation with documentation (the letter below).
The letter (disagree, in whole or part)
[Your name]
[Address]
[City, State ZIP]
[Daytime phone]
[Date]
Internal Revenue Service
[Use the address on your CP2000 response page]
Re: CP2000 - response (I disagree, in whole/part)
Name: [Your name] SSN/ITIN: [xxx-xx-1234]
Tax year / form: [year / 1040] Notice date: [date]
To whom it may concern:
I received the CP2000 proposing changes to my [year] return and I disagree with
the following item(s):
1. [Item, e.g. "1099-B proceeds of $[ ] from [broker]"]: The notice does not
reflect my cost basis of $[ ], so the taxable gain should be $[ ], not $[ ].
See attached [1099-B / brokerage statement].
2. [Item]: This income is already reported on my return at [line/schedule]; it
is being double-counted. See attached [copy of return page].
3. [Item]: [explanation]. See attached [document].
[If you agree with part:] I agree with the proposed change to [item] and have
indicated that on the enclosed response form.
Based on the above, the proposed additional tax should be reduced to $[amount /
zero]. I have enclosed the signed CP2000 response form and supporting documents.
Please adjust the proposed amounts accordingly and send confirmation.
Sincerely,
[Signature]
[Printed name]
How to send it
Use the response form and the fax number or address printed on the CP2000 (it often has its own return page). Send by certified mail with return receipt (or fax and keep the confirmation), attach copies (never originals), and keep a full copy. Respond by the deadline even if you’re still gathering one document — partial is better than missing it.
Notes. A CP2000 is not a final bill — you have rights — but ignoring it is how a manageable proposal becomes a Notice of Deficiency and then an assessed balance. If the change involves a forgotten 1099 you truly owe on, agreeing and arranging payment (plus asking about penalty abatement) is fine. General information, not tax advice.