The IRS Sent 1.6 Million CP2000 “Proposed Changes” Letters Last Year, and Most Were Triggered by a 1099 the Taxpayer Never Saw. The Letter Isn’t an Audit, and 30 Days Is the Window to Say So
A computer at the IRS matched your return against a form you never saw, and the clock on your response started the moment the envelope hit your mailbox. What happens next depends entirely on a single document most people throw…
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The envelope from the IRS arrives in the fall, and page one shows a balance due big enough to need a comma. For many retirees, that’s when panic sets in. A CP2000 letter means the IRS’s records and your return disagree, and the law gives you the first chance to say which one is right.
The IRS sent about 1.6 million of these “proposed changes” letters last year. Its own statistics show it closed 987,460 Automated Underreporter cases in fiscal 2025, which produced $5.9 billion in additional assessments. The response window printed on the letter is usually 30 days, or 60 days if you live outside the United States.
How a Computer Match Writes Your CP2000 Letter
The CP2000 comes from the IRS Automated Underreporter program. The program checks every W-2 and 1099 that payers file against the numbers on your return. A Treasury Inspector General for Tax Administration report found it routinely flags more than 20 million individual returns with discrepancies each year.
The IRS describes the letter as a proposal to adjust your income, payments, credits, and/or deductions. It comes from a computer match, and no auditor is assigned. Under section § 7522(b)(2), any notice “generated out of any information return matching program” has to explain its basis, so the letter names the exact form behind the change.
Common triggers include forgotten Forms 1099s and stock or crypto sales without basis. Sometimes the taxpayer never saw the triggering form. It went to an old address after a move, sat unopened in a brokerage’s online document center, or showed up as a corrected form after the return was filed.
A $40,000 Stock Sale Turns Into a $7,200 Proposed Bill
Consider a sample case: a retired couple in their late 60s who file jointly for 2024. Their other income puts their long-term gains in the 15% capital gains bracket. They sold an old stock holding for $40,000 and had paid $34,000 for it. Their broker had switched them to paperless statements, the 1099-B sat unopened online, and the sale never made it onto their return.
The broker reported the proceeds without the cost basis, so the matching program had nothing to subtract. It taxed the whole $40,000. A CP2000 can also propose the accuracy-related penalty, which equals 20% of the underpayment under 26 U.S.C. § 6662(a).
| Line | CP2000 Proposal | Correct Figure |
|---|---|---|
| Income added | $40,000 | $6,000 gain |
| Tax at 15% | $6,000 | $900 |
| 20% penalty | $1,200 | Figured on $900, if applied |
| Total before interest | $7,200 | $900 plus any penalty |
With the basis documented, the couple’s bill falls from $7,200 to about $900 plus interest. That’s a gap of $6,300, and closing it takes one brokerage statement.
Your 30-Day Window: Agree, Disagree, or Fix the Form 1099
- Identify the form. Check the payer and amount the letter lists against a wage and income transcript, which you can request on Form 4506-T or view in your IRS online account.
- If you agree, sign the response form and pay. When full payment isn’t possible, request a payment plan on Form 9465.
- If you disagree, the IRS tells you to state whether you agree or disagree with the notice and include any supporting documentation. Our couple would send trade confirmations showing their $34,000 basis.
- If the Form 1099 is wrong, contact the company that issued it. IRS guidance says the agency can’t correct an incorrect Form 1099-K, and a corrected Form 1099-R replaces the corresponding original.
Silence Turns a Proposal Into a Tax Court Deadline
Without a response, the IRS treats your silence as agreement. It finalizes the proposed changes and sends a statutory notice of deficiency by certified or registered mail under 26 U.S.C. § 6212(a). From that mailing date, you have 90 days, or 150 days if the notice goes to someone outside the United States, to petition the Tax Court. After that window closes, the IRS can assess the tax and start collecting.
Late letters come with one break. If you filed on time and the IRS didn’t send a notice saying your liability within the 36-month period that starts on the later of your filing date or the return’s due date, interest and certain penalties may be suspended for a limited period.
Expect slow replies. The IRS lost approximately 27% of its Examination and Collection staff from fiscal 2024 to fiscal 2025, according to the inspector general. Mail your response by certified mail, keep the receipt, and keep a full copy of everything you send.
One costly mistake is paying the proposed amount without checking it, especially when the trigger is a stock sale with no reported basis. If the letter involves several years or a large sum, it’s worth having a CPA, an enrolled agent or a credential tax professional check the math before the deadline printed on page one.
Contact [email protected] for any questions or corrections.
Vilma Rios is a tax professional and tax content contributor with more than 15 years of experience in tax and accounting. She specializes in federal tax research, tax education, and translating complex tax rules into clear, practical information for individuals, families, and small-business owners.
Vilma is a Content Tax Contributor II with the National Association of Tax Professionals (NATP), where she contributes to tax education and professional content. She has also presented tax information through webinars, including Spanish-language tax education, and has appeared on Telemundo 47 discussing tax topics and helping viewers understand important tax-filing requirements.
Her experience also includes tax and accounting work, tax research, IRS-related matters, and public tax education. While in college, Vilma volunteered in an IRS-sponsored tax assistance program and was recognized for her community service by local and state officials.
Known as “Your Tax Geek,” Vilma is passionate about making taxes easier to understand and helping people navigate an increasingly complex tax system.
