The control number on an IRS letter is a long numeric code, usually labeled “Control Number” or, on notices like the CP2000, “AUR control number.” It’s printed in the header of the first page next to your Social Security number, the tax year, and the notice number. Formally it’s called a Document Locator Number, or DLN, and it’s a 14-digit code the IRS assigns to every document that enters its processing system.1Internal Revenue Service. Section 4 – Document Locator Number It pinpoints your specific letter out of the millions the agency sends, which is why IRS staff ask for it when you call.
Control Number vs. Notice or Letter Number
Every piece of IRS correspondence carries at least two identifiers, and people mix them up constantly. The notice or letter number is the short code that names the type of letter. “CP2000” means the IRS found a mismatch between what you reported and what an employer or bank reported about you.2Internal Revenue Service. Understanding Your CP2000 Series Notice “LTR 12C” means the IRS needs more information before it can finish processing your return. That code identifies the template.
The control number identifies your copy. Thousands of people receive a CP2000 in a given year; each one has its own DLN tied to a specific taxpayer, tax year, and processing campus. When an agent needs to pull your exact file, the DLN gets them there fastest.
Where to Find It on the Page
The notice or letter number sits in the upper-right corner of the first page, usually inside a reference block that also lists the tax year, your SSN or EIN, and the response deadline.3Internal Revenue Service. Understanding Your IRS Notice or Letter
The control number is in the same header area on most modern notices. On a CP2000 it’s labeled “AUR control number.” It’s a long, unbroken string of digits, so it stands out from the shorter codes around it. On some older or less common correspondence it may appear in the footer instead. If you see a 14-digit number on the letter that isn’t your SSN or a dollar amount, that’s almost certainly the DLN.
What the 14 Digits Encode
The DLN isn’t random. Each segment carries routing information about where and when the document was created:1Internal Revenue Service. Section 4 – Document Locator Number
- Digits 1–2, the File Location Code, identify the IRS campus that processed the document.
- Digit 3, the Tax Class, indicates the type of tax, such as individual income or employment.
- Digits 4–5, the Document Code, identify the form or notice type.
- Digits 6–8, the Julian Date, record the processing date as a day of the year from 001 through 365.
- Digits 9–11, the Blocking Series, group related documents for batch processing.
- Digits 12–13, the Serial Number, distinguish individual documents within a batch, 00 through 99.
- Digit 14 is the last digit of the year the DLN was assigned, generated automatically.
You don’t need to decode any of this yourself. It’s here to explain why the number is so long and why every digit matters when an agent asks you to read it aloud.
Using the Control Number When You Contact the IRS
Having the DLN ready before you call speeds things up, but it doesn’t replace identity verification. The IRS will still confirm who you are through personal questions regardless of whether you have the control number in front of you.4Internal Revenue Service. Be Ready to Verify Your Identity When Calling the IRS Once you’re verified, reading off the control number lets the agent jump straight to your specific case instead of searching your account history.
If you’re responding by mail, the IRS tells you to write your Social Security number, the tax year, and the notice number on your payment and any correspondence.2Internal Revenue Service. Understanding Your CP2000 Series Notice Adding the control number helps the processing center match your response to the correct file. If the notice includes a tear-off response form, use it; the form already has the control number encoded. Send everything to the address printed at the top-left of the notice, not to a general IRS address.
What to Do If You Lost the Letter
Losing an IRS notice is common and doesn’t have to derail your response. Individual taxpayers can call 800-829-1040 (TTY/TDD 800-829-4059) and ask for details about the notice on file. Business taxpayers should call 800-829-4933.5Taxpayer Advocate Service. I Got a Notice From the IRS The agent can tell you what was sent, what it says, and the response deadline.
A faster option is your IRS Online Account at irs.gov. Once logged in you can view digital copies of notices the agency has sent, read the full letter, and pull the control number without waiting on hold.6Internal Revenue Service. Online Account for Individuals You can also request a tax account transcript, which summarizes recent activity and confirms what type of notice was issued, though it doesn’t reproduce the original letter.
Confirming the Letter Is Real
Before spending time chasing a control number, make sure the letter is legitimate. Scam letters have gotten convincing, and the most reliable check is to log in to your IRS Online Account and see whether the notice appears in your records.7Internal Revenue Service. Ways to Tell if the IRS Is Reaching Out or if It’s a Scammer If nothing shows up, the letter may be fraudulent. You can also call IRS customer service to confirm. If the letter turns out to be fake, report it through the IRS fraud reporting page, which has a dedicated link for fake letters, emails, texts, and calls.8Internal Revenue Service. Report Fraud Don’t send money or personal information in response to a letter you can’t verify.