A letter from an IRS Submission Processing Center almost always means something routine turned up while your return was being screened: a math correction, an unpaid balance, missing paperwork, or an identity check before a refund can go out. It is not an audit. The response is almost always the same three steps: find the CP or LTR number in the upper right corner, read what the notice asks for, and reply before the date printed on the page.
What the Letter Is Telling You
Submission Processing Centers handle intake and initial verification of returns. They receive filings, process payments, enter data, and run automated checks for errors or missing information. They do not conduct in-depth audits or interpret complex tax law. They catch surface-level problems: arithmetic that doesn’t add up, a missing signature, a payment that bounced, a form that wasn’t attached.
So if one of these centers has written to you, the trigger was almost certainly automated screening of your return, not a reviewer questioning your deductions or income sources.
One boundary worth knowing up front: the CP2000 notice, which flags mismatches between what you reported and what employers or banks told the IRS, does not come from a Submission Processing Center. It comes from a separate unit called the Automated Underreporter program. The response procedures are different, and they’re covered separately below because people often receive one alongside processing center mail.
Find Your Notice Number First
Every IRS notice carries a CP or LTR number, usually printed in the upper right corner of the first page. That number is the single most useful thing on the letter. Enter it on the IRS’s “Understanding Your IRS Notice or Letter” page at irs.gov and you’ll get a plain-language explanation of what the notice means and what you need to do.
Digital copies of many notices also appear under the “Notices and Letters” section of your IRS individual online account. Not every type is available there, so treat the online account as a supplement to the paper letter, not a replacement.
The Notices You’re Most Likely to See
A handful of notices account for most processing center mail. Knowing which one you have tells you whether the IRS wants money, wants documents, wants to confirm who you are, or is telling you a refund changed.
- CP11. The IRS corrected a math mistake on your return and you now owe more than you originally calculated, or your expected refund shrank.
- CP12. The IRS corrected a math mistake in your favor. You’re getting a refund you didn’t expect, or a larger one.
- CP13. The IRS corrected a math mistake and the changes wash out. No balance due, no refund.
- CP14. You have an unpaid balance of $5 or more. This is the most common IRS notice. It states the amount owed, including penalties and interest, and asks for payment within 21 days.
The CP11, CP12, and CP13 notices come from what the IRS calls “math error authority,” which lets the agency correct obvious calculation mistakes and assess additional tax immediately, without going through full audit procedures. That’s why the dispute window for these notices matters so much, as explained below.
Identity Verification Letters
If a return is flagged for identity verification, the IRS won’t finish processing it or release any refund until you confirm who you are. One of three letters will tell you how:
- Letter 5071C. Verify online through the IRS Identity Verification Service, available around the clock. You’ll need a government-issued photo ID and a copy of the return for the tax year in question.
- Letter 4883C. Call the toll-free number on the letter to verify your identity and return information by phone.
- Letter 5747C. Schedule an in-person appointment at a local Taxpayer Assistance Center.
If you did file the return, follow the instructions promptly. If you didn’t, the letter will explain how to report possible identity theft.
Missing Information Requests
Some letters simply ask for documents the IRS needs to finish processing your return: a missing W-2 or 1099, a schedule that wasn’t attached, a signature the return lacked. Processing stops until you supply what’s missing, so these deserve a quick response even though they aren’t assessing extra tax.
Deadlines You Cannot Miss
Every notice carries a response date, and the consequences of missing it depend on which notice you have.
For math error notices (CP11, CP12, CP13), you have 60 days from the notice date to request that the IRS reverse the adjustment. If you file an abatement request within that window, the IRS must undo the assessment by law. Miss it and the assessment becomes final; you generally lose the ability to challenge it in Tax Court.
For CP2000 notices, you typically have 30 days from the notice date. If the IRS doesn’t hear from you, it will issue a Statutory Notice of Deficiency, which starts a 90-day clock for filing a Tax Court petition. Responding inside the initial 30 days is far simpler than dealing with a deficiency notice.
For balance-due notices like the CP14, the letter usually sets a 21-day payment deadline. Penalties and interest accrue from the original due date of the return, not the notice date, so delay costs real money.
How to Respond
Read the entire notice, including the fine print on the back pages that most people skip. Compare every proposed change to your own records and your copy of the return. If the IRS says you earned $8,000 from a side job you never had, that’s a third-party reporting error worth disputing. If they caught a genuine arithmetic mistake, agreeing and paying is the fastest path forward.
What to Send
Send only what the notice asks for. If it requests a missing W-2, send the W-2, not your entire filing history. Include the response form or tear-off slip from the notice if one was provided, or a copy of the first page of the notice so the processing center can match your reply to your account. Write your Social Security number or Taxpayer Identification Number on every page of supporting documentation.
How to Send It
- Mail. Use the specific address printed on the notice, not the general IRS filing address. Send it certified with return receipt requested so you have proof of mailing and delivery dates.
- IRS Document Upload Tool. The IRS accepts electronic submissions for many notice types at irs.gov. You’ll need your notice number. This tool is for supporting documents, not for filing tax returns.
- Fax. Some notices, particularly CP2000, include a fax number. Faster than mail but without the same delivery confirmation.
Whatever method you use, keep copies of everything and note the date you sent it. A certified mail receipt is your best protection if the IRS later claims your response was late.
If You Disagree With the Notice
Agreeing when the IRS is right saves time and money. When they’re wrong, you have clear ways to push back.
Math Error Abatement
If you receive a CP11 or similar math error notice and believe the IRS made the mistake, request abatement in writing within 60 days of the notice date. By law, the IRS must reverse the assessment once it receives your request. Any later reassessment of the same tax has to go through normal deficiency procedures, which means a formal notice and the right to petition Tax Court before paying.
Disputing a CP2000
If a CP2000 proposes changes you disagree with, respond by the date on the notice with a signed statement explaining why, along with supporting documents. Common grounds for disagreement include income already reported on a different line of your return, offsetting deductions or expenses, or errors on third-party forms. If a form is wrong, contact the issuer and ask for a corrected one.
If the IRS doesn’t accept your explanation, you can request review by the IRS Independent Office of Appeals. Publication 5 explains how to prepare a formal protest.
If You Owe and Can’t Pay in Full
When a processing center notice reveals a balance due, penalties and interest are already running.
The failure-to-pay penalty is 0.5% of the unpaid tax for each month or partial month the balance remains outstanding, capping at 25%. With an approved installment agreement in place, the rate drops to 0.25% per month. If you ignore a final notice of intent to levy, it jumps to 1% per month. Interest compounds daily on top of the penalty. For the second quarter of 2026, the IRS charges 6% annual interest on individual underpayments, down from 7% in the first quarter.
An installment agreement spreads payments over time. Setup fees depend on how you apply and how you pay:
- Direct debit, applied online: $22
- Direct debit, applied by phone or mail: $107
- Other payment methods, applied online: $69
- Other payment methods, applied by phone or mail: $178
Low-income taxpayers pay reduced fees or have them waived. Applying online with direct debit is the cheapest route for everyone else. An installment agreement stops collection action, not the interest clock, so penalties and interest keep accruing on the remaining balance until it’s paid off.
When to Call the Taxpayer Advocate Service
Most processing center notices resolve with one response. If yours doesn’t, and the IRS keeps sending interim letters promising to look into it, or more than 30 days pass beyond normal processing time with no resolution, the Taxpayer Advocate Service may be able to step in. TAS is an independent organization within the IRS that helps taxpayers stuck in the system or facing hardship from an unresolved tax problem. Reach them through taxpayeradvocate.irs.gov or ask your local Taxpayer Assistance Center for a referral.