Letter 4883C
read it properlyLetter 4883C — identity verification by telephone
The same identity verification as the CP5071 series, with one operative difference: this one has no online path at all.
No day count is published.
If it passes. Until the IRS hears from you it will not process the return, issue a refund or credit any overpayment.
Why you got it
A return filed under your number needs verification.
What rights it carries
None conferred.
Do you have to respond?
Required.
The mistake people make
Trying to verify it online. There is no online option for a 4883C — call the Taxpayer Protection Program number printed on the letter. If phone verification fails you will be asked to bring documents to a local IRS office.
If crypto is why this arrived, the number on it is probably wrong.
Your exchange reports what you sold for and leaves the cost box blank, so any figure the IRS computes from it treats every coin as though it cost you nothing. Rebuild the basis from your own transaction history — free — and see the real number before the deadline above runs out.
Notices that arrive around this one
CP2006 — A receipt. The IRS has your correspondence and will tell you what it decides. CP5071 — A Form 1040 was filed under your number and the IRS wants to know whether it was you before it processes the return.Every notice in the library → Not sure it is really from the IRS? →
Sources: IRS — Understanding your letter 4883C. Retrieved 2026-08-28. Where the IRS publishes no day count we say so rather than repeat a number we cannot source — the date printed on your own notice is the one that governs. ClearBasis is tax software, not a tax adviser, and this is information rather than advice.