Short answer
Type the number printed in the right corner of your IRS letter, such as 566, CP2000 or LT11. The finder shows what the letter means, whether it belongs to an audit, a collection case or neither, and which guide explains your next step. Letters after the number matter: CP75 and CP75A are different notices.
Key takeaways
- The IRS prints the CP or LTR number in the right corner of every notice and letter; type it exactly, including any letters after the number.
- Audit letters (such as Letter 566, 525 or 950) mean the IRS is examining your return; collection notices (such as CP14, CP504 or LT11) mean tax is assessed and unpaid.
- A CP2000 is not an audit, but ignoring it leads to a CP3219A notice of deficiency, which carries a Tax Court deadline that cannot be extended.
- LT11 and Letter 1058 are the same final notice of intent to levy; both give you a limited window to request a Collection Due Process hearing.
- If your letter is not in the finder, look it up on the IRS notice page and call the IRS at a number listed on IRS.gov before you act on anything that looks suspicious.
Find your IRS letter by number
Type the number from your letter, notice or form and press the button. You can type it the way it is printed (“LTR 566”, “CP 75A”, “Form 4549”) or just the number (“566”). The finder covers 60 audit, collection and other IRS letters, notices and forms that have a full explanation on this site. Nothing you type is sent or saved.
How to read an IRS letter number
The IRS says you can find the CP or LTR number “on the right corner of the letter.” Most IRS mail carries one of four kinds of numbers:
| What you see | Examples | What to type | Good to know |
|---|---|---|---|
| CP plus a number | CP14, CP2000, CP75A | The whole code, for example cp75a | Letters after the number change the meaning: CP75, CP75A and CP75D are three different notices. |
| LTR or Letter plus a number | LTR 566, Letter 1058 | The number with any suffix, for example 566 or 2205-A | Suffixes matter here too: Letter 2202 sets an office audit appointment, while Letter 2202-B starts a mail audit. |
| LT plus a number | LT11 | lt11 | LT11 and Letter 1058 are the same final notice of intent to levy; Letter 1058 usually comes from a revenue officer. |
| Form number | Form 4549, Form 4564, Form 668-A | The form number, for example 4549 | Forms usually come enclosed with a cover letter, or are served on someone else, such as a notice of levy sent to your bank. |
If your envelope holds several pieces, look up the cover letter first. With an audit report, for example, Form 4549 and Form 886-A have no deadline of their own: the response date is on the cover letter, such as Letter 525 or Letter 950. Our audit letters guide shows the order in which audit letters usually arrive.
Audit, not an audit, or collection: what the stage tells you
Every result is tagged with one of three stages. The stage tells you what the IRS is doing and what kind of answer it wants.
| Stage | What is happening | Typical letters | Your first move | Read next |
|---|---|---|---|---|
| Audit | The IRS is examining your return: by mail, at an IRS office or in a field audit | Letters 566, 3572, 2202 and 2205-A to start; Form 4564 for records; Letters 525, 915 and 950 with the report; Letters 3219 and 531 as notices of deficiency | Send what is asked by the due date, or call before it to ask for more time | First steps after an audit letter |
| Not an audit | An automated notice: income others reported doesn’t match your return, a math error was corrected, or a return is missing | CP2501, CP2000, CP11, CP12, CP59, CP515, CP518, CP2566, and the CP3219A notice of deficiency | Compare the notice with your records and reply by the date on it | Types of IRS audits |
| Collection | The tax is assessed and unpaid | CP14, CP501, CP503, CP504, LT11, Letter 1058, CP90, Letter 3172, CP523, CP508C | Pay, set up a payment plan, or request a hearing before the deadline | I owe the IRS: what happens next |
“Not an audit” does not mean “not serious.” The Taxpayer Advocate Service says a CP2000 is not an IRS audit or a bill, but ignoring it leads to a CP3219A, a statutory notice of deficiency with a Tax Court deadline. The stages also connect: an audit you agree to, or a notice of deficiency you don’t answer, ends with the tax assessed and a bill such as a CP14, which starts the collection stage.
Letters whose deadlines you can't get back
Most IRS letters let you call and ask for more time. These do not, or missing them costs you a right you can’t recover:
| Letter | Deadline | What a missed deadline costs | Read next |
|---|---|---|---|
| Notice of deficiency: Letter 3219, Letter 531, CP3219A, CP3219N | 90 days from the date the notice is mailed to petition the U.S. Tax Court, or 150 days if it is addressed to you outside the United States (IRC 6213(a)); the IRS cannot extend it | Tax Court review without paying first | Notice of deficiency |
| Collection Due Process notices: LT11, Letter 1058, CP90, Letter 3172 | 30 days (IRS.gov, 2026) to request a hearing on Form 12153 (for a lien notice, the date printed on it) | The full hearing with Tax Court review; an equivalent hearing within 1 year (IRS.gov, 2026) of a levy notice gives no court review | Final notice action plan |
| 30-day letters: Letters 525, 915 and 950 | Generally 30 days from the letter date, set by the IRS | An Appeals conference before a notice of deficiency is issued | The 30-day letter |
| Math error notices: CP11, CP12 | The date on the notice | The formal right to have the change reversed | Dispute an IRS balance |
To count a 30-day or 90-day date, including the weekend and holiday rules, use the IRS audit deadline calculator. If a notice of deficiency prints a later last day to petition, that printed date controls.
If your letter isn't in the finder
The finder lists only letters we have a full guide for, so it does not cover every IRS notice. If yours is missing:
- Check the number again. Read the right corner of the first page and include any letters after the number.
- Look it up on IRS.gov. The IRS page Understanding your notice or letter lets you search by number or topic. The IRS says that if a letter doesn’t appear in that search or looks suspicious, call 800-829-1040 (IRS.gov, 2026).
- Check your IRS Online Account. The IRS makes certain notices and letters available there, and its audits page says audit status, letter dates and response due dates show under “Records and Status.”
- Rule out a scam. The IRS starts audits by mail and “won’t initiate an audit by telephone,” and payments go only to the United States Treasury. See how to spot a fake IRS letter.
- Respond by the date on the letter. Our IRS notices library and the step-by-step guide on how to respond to an IRS notice apply to almost any letter.
Answering the letter yourself, and when to get help
You can answer almost any IRS letter yourself: by mail, by fax, or through the IRS Document Upload Tool when the letter gives you an access code. Keep copies of everything you send and write down the date. Low Income Taxpayer Clinics represent eligible taxpayers in audits, appeals and collection cases for free or a small fee, and the Taxpayer Advocate Service (877-777-4778 (IRS.gov, 2026)) helps when an IRS problem is causing financial hardship.
A representative is worth considering when the letter is a notice of deficiency or a final notice of intent to levy, when several years or a large amount are involved, or when you are not sure which letter came first. An attorney, CPA or enrolled agent can take over the letters under a Form 2848. Global Gate Tax Relief offers a free consultation, tells you whether you can handle the letter yourself and, if it takes the case, quotes a flat fee upfront: request a free review or call 1-877-800-8180. No outcome is guaranteed.
Frequently asked questions
The IRS says the CP or LTR number is on the right corner of the letter, usually on the first page. Type it exactly, including any letters after the number, because CP75 and CP75A, or Letter 2202 and 2202-B, are different notices.
Yes. Both are the Final Notice of Intent to Levy and Notice of Your Right to a Hearing. Letter 1058 is usually sent by a revenue officer assigned to your case, and the LT11 by the IRS’s automated collection system. Either one gives you 30 days to request a Collection Due Process hearing.
No. A CP2000 proposes changes because income others reported doesn’t match your return; the Taxpayer Advocate Service says it is not an audit or a bill. You still need to reply by the date on the notice, or the IRS can send a CP3219A notice of deficiency.
All three start a mail audit of refundable credits such as the Earned Income Credit. A CP75 holds the credit part of your refund, a CP75A holds nothing because no refund is pending, and a CP75D also audits income and withholding and holds the full refund.
The notice of deficiency (Letter 3219, Letter 531, CP3219A, CP3219N): the Tax Court petition deadline cannot be extended by the IRS. The Collection Due Process window on an LT11, Letter 1058, CP90 or Letter 3172 is also fixed; after it you can only get an equivalent hearing without court review.
Check the number again, then search it on the IRS page “Understanding your notice or letter.” If it isn’t there or looks suspicious, call the IRS at 800-829-1040, not a number printed in the letter. Respond by the date on the letter either way.
The IRS starts audits by mail and says it won’t initiate an audit by telephone. Check your IRS Online Account, call the IRS at a number listed on IRS.gov, and never pay anyone except the United States Treasury. Gift card or wire demands are a scam.
Sources
- IRS: Understanding your IRS notice or letter (reviewed 25-Oct-2026)
- IRS: IRS audits
- IRS Independent Office of Appeals: Letters and notices offering an appeal opportunity
- Taxpayer Advocate Service: Letter 566 series (initial contact)
- Taxpayer Advocate Service: Notice CP2000
- IRS: Understanding your CP75 notice
- IRS: Understanding your CP11 notice
- IRS: Understanding your LT11 notice or Letter 1058
- IRS: Understanding your CP3219A notice
- 26 U.S.C. 6213, Restrictions applicable to deficiencies; petition to Tax Court
- 26 U.S.C. 6330, Notice and opportunity for hearing before levy
- IRS: How to know it's the IRS
- IRS: Low Income Taxpayer Clinics
We check every figure against IRS.gov and log changes on the key figures page.
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This page is general information about IRS rules, not tax or legal advice for your situation. IRS figures change; each one links to its official source and the date we last checked it.