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IRS notice decoder · Proposed changes to a return

4800C: the IRS is proposing a change to your return

A 4800C proposes a change to your return. Read the changes, decide if you agree, and send the response form by the date the IRS gives.

By the Carry Forward Learning team Reviewed by Hunter Nottingham, JD, CPA

No dated figures Checked Review by

CheckedOct 19, 2026

What a 4800C means

A 4800C is a proposal, not a final bill. The IRS says it's proposing a change to your tax return, and the letter has a section called Changes to Your Return that shows what. source 1

The IRS says being selected doesn't mean you made an error or were dishonest. source 1

We treat it like any proposal: read the details, compare them to your return, and answer with paper, not a phone call alone.

The date that counts

The IRS page gives a set number of days from the date of the letter to return the Response Form, and the letter prints the date. If you don't answer, the IRS says it will send another notice asking for documents or explaining the adjustments. source 1

Why people get one

  • Something on the return, often a credit or withholding, needs support the IRS doesn't have yet.
  • The IRS picked the return for a check that income, expenses and credits are reported right. source 1
  • Rarely, someone else filed using your information. source 1

First steps

  1. Pull your return for the year on the letter and read the Changes to Your Return section beside it. source 1
  2. Decide whether you agree. If you disagree, gather the supporting documents the letter lists. source 1
  3. Reply through the IRS Documentation Upload Tool, which the IRS calls the fastest way, with a signed, dated copy of the letter marked agree or disagree. Reach it by typing irs.gov in yourself. source 1
  4. Or fax using the number in the letter, or mail it in the enclosed envelope. source 1
  5. Check your IRS online account (typed in at irs.gov) and keep copies of everything you send.

What not to do

  • Don't ignore it. The IRS says the next notice will explain adjustments to your tax, withholding and credits. source 1
  • Don't upload documents through a link in an unexpected email or text. Type irs.gov yourself.
  • Don't send originals; send copies.
  • Related CP2000 A different proposed-change notice, built on income that payers reported to the IRS.
  • Related LTR 12C A request for missing information before a return is processed.

Questions

How do I respond to a 4800C?

The IRS recommends its Documentation Upload Tool, with a signed, dated copy of the letter showing whether you agree, plus the upload form. Fax and mail are options too. source 1

What happens after I answer a 4800C?

The IRS says it will contact you if it has questions, and that otherwise no action is needed. The page also gives a typical review time. source 1

I didn't file the return the 4800C is about. What now?

The IRS says someone may have filed without your consent and points you to Form 14039, Identity Theft Affidavit, and its Identity Theft Central page. source 1

Sources

  1. IRS, Understanding your letter 4800C (updated January 30, 2026) (external site) checked Oct 19, 2026

Every rule on this page comes from the IRS page in the list, read on the date shown. Your notice itself is the final word on its own dates and amounts.