IRS Notice Library

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New or changed in the last 12 months

Letter 105-CUpdated — new disallowance reason
The IRS is denying an entire ERC claim and starting the two-year clock to appeal or sue for it.
CP081BNewly digital in Business Tax Account
The IRS is holding payments or credits for a business return it never received, and the refund statute is running out.
CP134RNewly digital in Business Tax Account
A mismatch between a business's deposits and its return left it owed a refund.
CP211ANewly digital in Business Tax Account
Confirmation that a Form 8868 extension (exempt organization or Form 5330) was approved.
CP575New digital notice
A downloadable digital confirmation of an entity's EIN, accepted by banks in place of the paper CP575 or Letter 147C.
CP320BNew notice
The IRS is telling an ERC claimant with six months or less left on their two-year suit clock that they can request more time using Form 907.
Letter 106-CUpdated
The IRS is denying part of an ERC claim (or all the ERC but allowing other return changes) — same two-year suit clock as full disallowance.
CP53EUpdated procedure
The IRS owes a refund it cannot deposit and wants updated bank information within 30 days, or a self-service waiver reason if the taxpayer has none.
Letter 6612Newly primary-sourced
The IRS is auditing an ERC claim and holding the credit pending the results.

This library covers 127 notice codes. Some codes share one page (LT11, Letter 1058, CP90, and CP297 below are one page).

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 and high-volume, so check each one against the return. The human-issued ones carry more weight and less room to argue you were simply matched incorrectly.

Response deadlines vary from 10 days to 90 days (150 outside the United States); read yours. CP2000 gives 60 if you live abroad. The hearing window on LT11 and Letter 1058 stays 30 days. Each window runs from the date printed on the notice, not the date you received or opened it. A narrow set of notices, most importantly the Statutory Notice of Deficiency (CP3219A), carry a 90-day deadline instead (150 days if addressed outside the United States), set by statute. File on time: the Tax Court has dismissed late petitions for lack of jurisdiction, however strong the case, though the Third Circuit held in 2023 that the deadline is not jurisdictional (Culp v. Commissioner).

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 readers ask about most

Each of these five starts a collection sequence, moves money inside an account, or gets mistaken for a notice that does one of those. Read the one you are holding first.

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.

Notices with a deadline or a trap

CP3219A and LT11/Letter 1058 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. The four Taxpayer Protection Program letters (5071C, 4883C, 5747C, 6330C) work differently: they hold a refund back for as long as identity verification takes. For 5071C, 4883C and 6330C, the National Taxpayer Advocate reports that the Taxpayer Protection Program phone line answered 19% of calls during the 2026 filing season through April 18. The four Automatic Exemption from Penalty notices (CP95, CP95(SP), CP195B, CP895(b)) tell a taxpayer the IRS granted penalty relief. Their pages explain what each letter means. Each gets the same depth as the notices above.

Notice	What it's about
CP3219A	Statutory Notice of Deficiency — the 90-day Tax Court petition clock (150 days outside the United States), set by statute.
LT11 / Letter 1058	Final Notice of Intent to Levy — the notice that actually authorizes wage and bank levy and opens the 30-day Collection Due Process (CDP) window.
Letter 5071C	Identity verification with an online option — the most widely issued TPP letter, and the only one of the four that can be finished without a phone call.
Letter 4883C	Identity verification by phone only — no online option, and one of the hardest IRS lines to get through on.
Letter 5747C	Verify your identity in person at a Taxpayer Assistance Center. If you did not file the return, call the Taxpayer Protection Program number on the letter.
Letter 6330C	A limited-pilot identity-and-return verification letter processed identically to 4883C — unrelated to IRC §6330.
CP95	The IRS granted automatic penalty relief and is telling you so — good news. The IRS says AEP needs no action from the taxpayer.
CP95(SP)	CP95(SP), the companion notice to CP95 that the Procedural Update lists beside it — automatic penalty relief. The IRS says AEP needs no action from the taxpayer.
CP195B	The business-account version of CP95 — the IRS granted automatic penalty relief, and no response is required.
CP895(b)	The other business-account version of the automatic-penalty-relief notice — the IRS does not say what separates it from CP195B.
CP161	The business balance-due notice — and not always a penalty notice at all. What the billing summary actually breaks down.
CP162	A partnership's e-filing-failure penalty — not the late-filing penalty most practitioners assume. That one is CP162A.
CP162A	The late-filing penalty for a partnership or S corporation — up to 12 months of per-owner exposure, and relief that depends on which entity type got the notice.
CP162B	An incomplete-return or e-filing penalty for a partnership or S corporation — First-Time Abate reaches at most one of the two, depending on entity type.
CP162C	The broadest notice in the CP162 family — late filing, an incomplete return, a missing tracking report, or an e-filing failure, sometimes more than one at once.
CP10	Shrinks the estimated-tax credit you carried forward to next year, not this year's balance — the math-error notice most likely to be misread as good news and filed away.
CP13	A math-error notice with nothing to pay and no refund coming — the correction nets to near zero, but the 60-day right to dispute it works exactly like CP11's.
CP101	A Form 940 math-error balance due with a 10-day response window — a fraction of the 60 days individual taxpayers get on a comparable notice, and the gap isn't a typo.
CP102	The employment-tax (941/943/944/945) math-error balance-due notice — same tight 10-day window as CP101, different return entirely.
CP107	A Form 1042 withholding math-error balance due, with a 60-day window and a failure-to-deposit penalty most of this notice family never carries.
CP111	The refund-side mirror of CP101 (Form 940) — no action required, just a refund to confirm.
CP112	The refund-side mirror of CP102 (the 941/943/944 family) — no action required, just a refund to confirm.
CP117	The refund-side mirror of CP107 (Form 1042) — and the one overpayment notice in this family that still carries a 10-day deadline.
CP268	The IRS holding a business's excess credit pending instructions, tied to a math-error posting — 30 days to say refund it or apply it elsewhere.
CP565	The IRS confirming your ITIN — nothing to pay and nothing to send back unless your name or date of birth is wrong, but an ITIN unused on a return for three years expires.
LT36	A one-time 2025 reminder letter to federal employees and retirees with an unpaid balance or unfiled return — not a levy notice, and about 427,000 were mailed, not the 525,000 widely reported.
Letter 3064C	The IRS's all-purpose custom reply letter — an employee writes the body for one taxpayer, so the code says nothing about what the letter is about.
Letter 3219	Statutory Notice of Deficiency after a mail audit — 90 days to petition the Tax Court (150 outside the United States), set by statute.
Letter 531	Statutory Notice of Deficiency after an in-person audit — the same 90-day Tax Court clock, usually with Form 4089-B as the waiver.
Letter 3219-B	Statutory Notice of Deficiency for a corporation, estate, or trust after a Business Master File (BMF) Underreporter review, often following Letter 2030.
CP59 / CP259 / CP518 / CP518B	The IRS's unfiled-return notices — CP59, CP515, CP516 and CP518 for individuals, CP259 and CP518B for businesses — and where each sits in the escalation.
CP63 / CP2566 / CP2566R / CP3219N	The IRS's calculated-balance notices for an unfiled return — CP63 refund hold, CP2566 and CP2566R proposed amounts, and the CP3219N 90-day letter — as one escalation.
CP30	The IRS increased your estimated tax penalty above what you reported — usually a smaller refund, not a bill.
CP30A	The IRS reduced or removed an estimated tax penalty you reported — CP30's reversal pair, and generally no action required.
CP2501	The Automated Underreporter (AUR) inquiry that can precede a CP2000 — the IRS asks for an explanation and has not yet proposed an adjustment. A reader who treats it like an audit or like CP2000 itself responds the wrong way.
Letter 3172	The Notice of Federal Tax Lien filing and Collection Due Process (CDP) hearing rights — a 30-day clock that starts the day after the 5-business-day period that follows the lien filing, not the letter date.
Letter 2030	CP2000's business counterpart, for Form 1120 and Form 1041 filers only — a different accuracy-penalty threshold and a different escalation letter than the individual notice.
CP91 / CP298	The final warning before the IRS starts taking 15% of Social Security benefits every month — issued only after an earlier notice already carried the appeal rights.
Letter 1153	The Trust Fund Recovery Penalty proposal — a 100% personal penalty under IRC §6672, with a 60-day (75 outside the US) protest deadline that forecloses the pre-assessment appeal once missed.
CP06	A real audit of your Premium Tax Credit claim, with a refund hold attached — not a routine matching notice like CP2000.
CP11A	What plain CP11 becomes automatically when an EIC disallowance traces to a Social Security number, name, or date-of-birth mismatch — a different fix than a routine recalculation.
CP39	A refund taken from you, your spouse, or a former spouse for a joint balance — not simply an offset to a different tax year. That distinction opens relief options CP49 doesn't.
CP62	A payment applied to your account — outcome-neutral, despite its reputation as always-good-news. The same format covers a refund, a zero balance, and a real bill.
CP14I	CP14's IRA-specific sibling — a missed required minimum distribution or an excess contribution, not the early-withdrawal penalty most practitioners assume.
CP25	CP24's even-balance sibling — the discrepancy was too small to bill or refund, and disputing it doesn't carry the formal abatement right other math-error notices do.
Letter 2531	CP2501's business counterpart for Form 1120 and Form 1041 filers — its own response form, no confirmed dollar threshold, and a narrower scope than "any business" implies.
CP320B	The IRS flags a real option — Form 907 — for an Employee Retention Credit (ERC) claimant with six months or less left on the IRC §6532 two-year suit deadline. The notice does not extend the deadline by itself.
Letter 105-C	A full Employee Retention Credit (ERC) claim disallowance — and a two-year clock to sue for it that keeps running whether or not an appeal is still pending.
Letter 106-C	A partial Employee Retention Credit (ERC) claim disallowance — the same two-year suit deadline as a full disallowance, applied only to the denied portion.
CP575 (digital)	A downloadable EIN confirmation inside Business Tax Account — a faster substitute for a lost paper CP575 or a Letter 147C phone request.
CP081B	The IRS is holding a business's credits with no return filed to claim them — and the refund statute, generally three years from the return's due date, is running out.
CP30B	An estimated tax penalty automatically capped at its legal maximum — no response needed unless you disagree with the reduced figure.
CP211A	Confirms a Form 8868 filing extension (exempt organization or Form 5330) was approved — payment deadlines and other clocks on the same return are unaffected.
CP134R	A federal tax deposit discrepancy resolved in a business's favor — CP134B's balance-due mirror image.
Letter 6612	The IRS is auditing an Employee Retention Credit (ERC) claim and holding the credit until the review concludes — earlier in the process than a disallowance letter, not proof of one.

Tier 2 — the next twenty by search volume

Each of these 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. They're listed as codes rather than a description table because this library only publishes a summary line once it exists on the real page — click through to read it rather than a blurb here.

Everything else

31 more letter-format notices have no page yet, and this library has not ranked them. The lookup box above searches only the notices listed on this page.