How to read an IRS notice comes down to reading it in the right order. Start with the notice number, a code beginning with CP or LTR that the IRS says appears "on the right corner of the letter." Look that number up in the IRS notice search on IRS.gov, which explains why that type of notice is sent. Then read the notice itself for three things: the reason it was sent, any amount or change to the return, and the date printed on the notice by which to act. That date, not a general rule, is the deadline that applies.
This guide walks through that order and explains what the most common notices are asking for. It is general information about how federal tax notices are organized, not an interpretation of any particular letter. A specific notice about a specific return is a question for a tax professional, and the IRS pages cited below are the controlling sources.
Why the notice number comes first
A notice from the IRS can look like a wall of text, and the instinct is to read it top to bottom looking for a dollar figure. The faster route is the code in the corner. The IRS page Understanding your IRS notice or letter (last updated May 26, 2026, read September 27, 2026) tells readers to "find the CP or LTR number on the right corner of the letter," and offers a search where a notice can be looked up "by number or topic."
The number matters because the same notice number is sent for the same reason to everyone who receives it. Looking it up first tells the reader what kind of letter this is before the details of the specific account come into it. The reader then knows whether the letter is a bill, a correction, a question or a request for documents, and reads everything else in that light.
CP versus LTR
Notice numbers start with one of two prefixes. The IRS page refers to them as "CP or LTR" numbers: CP numbers are notices, and LTR numbers are letters. For a reader, the practical difference is small. Both are official correspondence, both can carry a date to act by, and both are looked up in the same search.
The three things to read on the notice itself
Once the notice type is known, the notice itself answers three questions.
1. Why it was sent
The IRS notice page lists the general reasons it writes. It may contact a taxpayer if:
- "you have a balance due"
- "your refund has changed"
- "we have a question about your return"
- "we need to verify your identity"
- "we changed or corrected your return"
Nearly every notice fits one of those five. Matching the notice to one of them is the single most useful step in reading it, because each reason calls for a different kind of attention.
2. What amount or change it describes
A balance due notice states what is owed. A correction notice explains what was changed on the return. A proposed change describes an adjustment the IRS has not yet made final. The IRS page advises comparing the notice's information with the original return, so the filed return for the tax year named on the notice is the document to have open alongside it.
3. The date to act by
This is the part most worth finding before anything else is done. The IRS notice page says: "If we ask you to respond, act by the due date," and "To guarantee your appeal rights, reply by the due date." The date to use is the one printed on that notice. Different notices carry different windows, and no single number of days applies to every IRS letter.
What common notices are asking for
Three frequently discussed notices show how different the requests can be. Each summary below comes from the IRS's own page for that notice, read September 27, 2026.
| Notice | What the IRS says it is | What the IRS says about responding |
|---|---|---|
| CP14 | "You owe money on unpaid taxes" | Pay the amount owed by the due date on the notice; interest accrues after that date and a late payment penalty applies |
| CP12 | "We corrected one or more mistakes on your tax return," changing a refund or creating one | No response needed if the taxpayer agrees; if not, contact the IRS by the date on the notice |
| CP2000 | A difference between the return and third-party records | "This notice isn't a bill and your response may be required" |
CP14: a balance due
The IRS page Understanding your CP14 notice (last reviewed June 23, 2026) explains that the notice states how much is owed and how to pay it. It says that "interest accrues on the unpaid amount after that date" and that a late payment penalty applies. A CP14 is a bill for a balance the IRS already shows on the account.
CP12: a correction the IRS already made
The IRS page Understanding your CP12 notice (last reviewed August 11, 2026, read September 27, 2026) describes a notice sent after the IRS "corrected one or more mistakes" on a return. If the taxpayer agrees, "no response is required." If not, the page says to contact the IRS "by the date shown on your notice," and warns that missing that date means losing "formal rights to have the change(s) reversed." This is the clearest example of why the date on the notice matters more than the size of the change.
CP2000: a proposed change from matching
The IRS page Understanding your CP2000 notice (last reviewed July 14, 2026) describes a notice sent when income or payment information from employers or financial institutions does not match the return. It is not a bill, and the IRS describes the process as a review by mail rather than an audit. The proposed change can raise the tax, lower it or leave it unchanged. The notice carries its own response date.
The four responses the IRS describes
The IRS notice page groups the reader's position into four situations:
- If the notice is agreed with: the IRS says to "take any requested action" and that "you don't need to reply unless we specifically ask you to."
- If the notice is disputed: the IRS says to follow the instructions in the notice and "include information and copies of documents for us to review."
- If money is owed: "Even if you can't pay the full amount you owe, pay by the due date. This can reduce interest and penalty charges."
- If the IRS made corrections: compare the notice with the original return and keep the corrected copies.
In every case, the IRS also says to "review it carefully and keep it for your records." A notice is part of the paper trail for that tax year, in the same way an insurer's documents are. Readers who have worked through an explanation of benefits, line by line or an insurance declarations page will recognize the approach: identify the document type, find the figures that matter, then find the date.
Is the notice real?
The same IRS page says that if a letter "doesn't appear in your search or if it looks suspicious, call 800-829-1040," and states that the IRS does not start contact by email or text message. That gives a reader two checks: whether the notice number exists in the IRS search, and whether the contact came by mail. The page also notes that certain notices and letters can be viewed in the IRS online account, which is a third way to confirm a notice is genuine without using any phone number printed on the letter itself.
A reading checklist
A short sequence that follows the IRS's own guidance:
- Find the CP or LTR number in the right corner.
- Look it up in the IRS notice search.
- Identify which of the five reasons applies.
- Find the tax year and compare the notice with that year's return.
- Find the date to act by, printed on the notice.
- Note the contact number in the notice's information section.
- Keep the notice with that year's tax records.
When to involve a professional or an advocate
Reading a notice is one step; deciding whether to agree, dispute or pay is a decision about a specific return, and that is for a tax professional such as a CPA, an enrolled agent or a tax attorney. Any of them will ask first for the notice itself with its notice number, then the filed return for that tax year, the W-2s, 1099s and other records behind the figures in question, and any earlier letters about the same issue. For problems that are not resolved through normal IRS channels, the IRS points taxpayers to the Taxpayer Advocate Service, which it calls "Your Voice at the IRS." A notice from a state tax agency follows that state's own rules, and the state's department of revenue is the contact for it.
Frequently asked questions
Where is the notice number on an IRS letter?
The IRS says the CP or LTR number is "on the right corner of the letter." That number can be entered in the notice search on IRS.gov to see what that type of notice means.
Does every IRS notice need a reply?
No. The IRS says that if a taxpayer agrees with a notice, "you don't need to reply unless we specifically ask you to." A notice that asks for a response, or one the taxpayer disagrees with, has a date printed on it to act by.
How long is there to respond to an IRS notice?
There is no single answer. Each notice states its own date. The IRS says to act by the due date on the notice to guarantee appeal rights, and the CP12 page warns that missing its date means losing formal rights to have the change reversed.
Is a CP2000 an audit?
The IRS says a CP2000 "isn't a bill" and describes it as a review of the return by mail rather than an audit. It proposes a change based on third-party records and may require a response.
How can a notice be checked as genuine?
The IRS says to call 800-829-1040 if a letter does not appear in its notice search or looks suspicious, and states that it does not start contact by email or text.
IRS notice procedures change. The details in this article were checked against IRS sources on September 27, 2026.
