IRS Notice Library
This library covers 85 notices — a code-coverage figure, not a page count. Some of those codes are the same notice under different labels (LT11, Letter 1058, and CP90 below are one page for exactly that reason), so the number of pages you'll find here is smaller than 85 even though every one of the 85 codes is accounted for.
Every IRS notice starts life one of two ways: generated automatically by a matching program that compares your return against data the IRS already has, or issued after a human — a Revenue Officer, an Appeals officer, an examiner — has actually looked at your case. That distinction matters more than the notice's letter or CP number. A CP2000, for example, comes out of an automated matching program running against millions of returns at once; a Letter 1058 comes from a Revenue Officer who has your file open. The automated notices are fast, high-volume, and wrong often enough to be worth checking every time. The human-issued ones carry more weight and less room to argue you were simply matched incorrectly.
Response deadlines follow a similar pattern. Most IRS notices — CP2000, CP504, the levy notices — give 30 days from the notice date (60 days if the address on file is outside the United States), and that window is measured from the date printed on the notice, not the date it was actually received or opened. A narrow set of notices, most importantly the Statutory Notice of Deficiency (CP3219A), carry a 90-day deadline instead, and that one is jurisdictional: file even one day late and the U.S. Tax Court has no authority to hear the case at all, no matter how strong it is.
The notice number itself is a genuinely useful clue. "CP" numbers (CP14, CP2000, CP504, CP3219A) are computer-generated — the "C" stands for computer-issued. "LT" and plain "Letter" numbers (LT11, Letter 1058) more often signal a specific IRS function or, in Letter 1058's case, a Revenue Officer working the case directly, even though LT11 and Letter 1058 end up granting the identical rights. Learning to read the prefix, not just memorizing what each individual number means, is what lets a practitioner correctly triage a notice they've never seen before.
Tier 1 — the notices people actually receive
These five arrive in more mailboxes than anything else in this library, and each one either starts a collection sequence, moves money inside an account, or gets mistaken for a notice that does. Read the one you are holding before you do anything else with it.
| Notice | What it's about |
|---|---|
| CP24 | The IRS recalculated your estimated tax payments and found money in your favor — the refund notice that says no response is required. |
| CP14 | The first balance-due notice — notice and demand under IRC §6303, and the start of the collection sequence. |
| CP53E | The IRS owes you a refund it cannot deposit — and needs bank details within 30 days. Widely mistaken for a scam. |
| CP2000 | Notice of underreported income — a proposed adjustment, not a bill. |
| CP504 | Notice of intent to levy your state tax refund — the first levy notice, not the final one. |
Written in full for a different reason
Fewer people go looking for these two, and that is part of the problem. Both carry a deadline that ends a right permanently when it passes — the 90-day Tax Court petition window, and the 30-day Collection Due Process window — so this library covers them in the same depth as the notices above despite how rarely they arrive.
| Notice | What it's about |
|---|---|
| CP3219A | Statutory Notice of Deficiency — the 90-day Tax Court petition clock that nobody can extend. |
| LT11 / Letter 1058 | Final Notice of Intent to Levy — the notice that actually authorizes wage and bank levy and opens the 30-day CDP window. |
Tier 2 — queued for full write-ups
These are next. Each one gets the same treatment as a Tier 1 notice — what triggered it, the real deadline, the practitioner's next step, and what it gets confused with — rather than a summary line. Listing them as codes now, and describing them only once the page exists, keeps this library from claiming to explain something it has not checked yet.
One more sits outside that ranking. It holds a URL this library reserved before the search data existed, and the data never turned it up:
Everything else
A further eight notices — CP06, CP11A, CP297, CP298, CP39, CP62, CP91, CP14I — turn up rarely enough that a separate page for each would be a page nobody reads. A single category page will cover them together rather than one at a time. That page does not exist yet, which is why nothing here links to it.
Beyond the CP numbers, 47 letter-format notices are also in scope. Where those belong in the order above is genuinely unknown right now — the search data behind every grouping on this page covers CP numbers only, and the letter-format research is still pending. They sit here as outstanding work rather than in a tier somebody guessed at.