IRS Stop 6525 is an internal mail routing code that sends your response to a compliance unit at the Kansas City, Missouri, Submission Processing Center.1Internal Revenue Service. Notice CP39 If a notice told you to write to this address, the IRS has flagged something on your individual return and is holding processing until you send supporting documents. The single most common request is documentation for the Premium Tax Credit, but the unit also handles refund offsets, disputed payments, and certain penalty issues.
Which Notices Route Here
You’ll only be writing to Stop 6525 because a notice told you to. Check the notice number in the upper right corner of your letter; the response depends on which one you received.
- CP06 or CP06A: the IRS is holding part of your refund and needs documentation to verify the Premium Tax Credit you claimed.2Internal Revenue Service. Understanding Your CP06/CP06A Notice
- CP39: a refund from you, your spouse, or a former spouse was applied to a past-due balance, and you may still owe more.3Internal Revenue Service. Understanding Your CP39 Notice
- CP60: the IRS removed a payment it believes was credited to your account by mistake, leaving a new balance due.4Internal Revenue Service. Understanding Your CP60 Notice
The unit at Stop 6525 belongs to Submission Processing Compliance and Integration Services.5Internal Revenue Service. Notice CP60 It reviews individual returns that automated systems flagged for discrepancies between what you reported and what the IRS has on file. Do not send an original tax return here.
Premium Tax Credit Responses
Most people writing to Stop 6525 are answering a Premium Tax Credit question. If you bought coverage through a Marketplace and received advance payments during the year, you have to reconcile those advance payments against the final credit you actually qualify for at filing time.6Internal Revenue Service. Reconciling Your Advance Payments of the Premium Tax Credit Form 8962 does that reconciliation.7Internal Revenue Service. Instructions for Form 8962
If you filed without Form 8962, or the numbers on it don’t match your Form 1095-A from the Marketplace, the IRS holds part or all of your refund and sends a notice. To resolve it, complete Form 8962, attach a copy of your Form 1095-A, and mail everything to Stop 6525.7Internal Revenue Service. Instructions for Form 8962
If your final credit is smaller than the advance payments you received, you owe the difference back.8Internal Revenue Service. Questions and Answers on the Premium Tax Credit For 2025 and earlier tax years, repayment was capped for households earning under 400 percent of the federal poverty line, with caps ranging from $375 to $3,250 depending on income and filing status.9Centers for Medicare & Medicaid Services. Are There Limits to How Much Excess Advance Payments of the Premium Tax Credit Consumers Must Pay Back
Other Documents the Unit Handles
Income and Deduction Verification
If the notice asks you to verify income or deduction figures, send copies of W-2s, 1099 forms, or schedules that support the business expenses or itemized deductions you claimed. Send clear, legible copies, never originals.
Payment Disputes
A CP60 notice means the IRS removed a payment it believes was applied to your account by mistake.4Internal Revenue Service. Understanding Your CP60 Notice If the payment was in fact yours, mail proof to the address on the notice: a canceled check, a bank statement showing the debit, or a payment confirmation.
Penalty Abatement
If the notice includes a penalty and you had a legitimate reason for the underlying problem, you can request abatement. The IRS looks at whether you exercised ordinary care but still could not comply on time. Serious illness, natural disasters, and inability to obtain records generally qualify. Simple mistakes, not knowing the rules, or relying on a tax preparer who got it wrong generally do not.10Internal Revenue Service. Penalty Relief for Reasonable Cause Your written explanation should describe what happened, when, and how it prevented compliance. Attach evidence: medical records, insurance claims, official disaster declarations.
What Every Response Needs
Whatever the notice, include the same baseline items in every package: a copy of the notice you’re answering (it carries internal tracking codes the unit needs), your Social Security Number on every page, the tax year in question, and each specific document the notice requested. Missing even one requested item often restarts the clock.
How to Send Your Response
By Mail
The mailing address is:
Internal Revenue Service
Stop 6525
Kansas City, MO 64999-00251Internal Revenue Service. Notice CP39
Use USPS Certified Mail with Return Receipt Requested. The postmark date counts as your filing date under IRC Section 7502, so a timely postmark protects you even if the envelope arrives after a deadline.11Office of the Law Revision Counsel. 26 USC 7502 – Timely Mailing Treated as Timely Filing and Paying
You can also use an IRS-designated private delivery service from FedEx, UPS, or DHL, but only specific service levels qualify for the timely-mailing rule. Check the IRS list before choosing.12Internal Revenue Service. Private Delivery Services (PDS) Private carriers can’t deliver to P.O. Boxes, so use the physical street address: Internal Revenue Submission Processing Center, 333 W. Pershing, Kansas City, MO 64108.13Internal Revenue Service. Submission Processing Center Street Addresses for Private Delivery Service (PDS)
Include a short cover letter listing each enclosed document and referencing the notice number. Keep a complete copy of everything, and save the tracking number or certified mail receipt.
Through the Document Upload Tool
The IRS Document Upload Tool accepts scanned or photographed documents and gives you an immediate on-screen confirmation.14Internal Revenue Service. IRS Document Upload Tool You’ll need the notice or letter number, your name as it appears on the notice, and your Social Security Number. Files must be JPG, PNG, or PDF, up to 15 MB each.15Internal Revenue Service. Interim Guidance on the Mandatory Use of Digital Tools for Field Collection Employees The tool doesn’t accept tax returns, but it works for Form 8962, W-2 copies, identity verification paperwork, and other supporting documents.
If You Don’t Respond
Silence is the most expensive choice. On a Premium Tax Credit notice, if the IRS doesn’t hear from you within 30 days of the notice date, it will disallow the credit entirely and send an updated audit report with proposed changes: additional tax, penalties, and interest.2Internal Revenue Service. Understanding Your CP06/CP06A Notice
If you still don’t respond, the IRS eventually issues a Statutory Notice of Deficiency, sometimes called a 90-day letter. It starts a hard clock: 90 days to petition the U.S. Tax Court, or 150 days if you live outside the United States. Miss it and you lose the right to challenge the assessment in court without first paying the disputed amount.16Taxpayer Advocate Service. Letter 3219-C Statutory Notice of Deficiency After that, the IRS assesses the tax and begins collection, which can include levying bank accounts and garnishing wages.
Tracking and Follow-Up
Don’t expect a quick reply. The IRS publishes a processing status page showing which months of correspondence it’s currently working through, and backlogs of several months are common.17Internal Revenue Service. Processing Status for Tax Forms Carrier tracking confirms delivery; the upload tool gives an on-screen receipt. The IRS itself won’t acknowledge your documents until it actually reviews them.
Once the review is done, you’ll get one of three outcomes: a notice confirming an adjustment in your favor, a notice that the proposed changes stand with instructions for next steps, or a request for additional documentation. If 60 days have passed and the processing status page suggests the IRS should have reached your correspondence, call the number printed on your original notice. Have your submitted copy and tracking number in front of you.
When to Call the Taxpayer Advocate Service
If your case has stalled more than 30 days beyond the normal window, or the delay is causing real financial hardship, the Taxpayer Advocate Service may be able to intervene. TAS is an independent organization within the IRS. Qualifying situations include an immediate threat of adverse action like a levy, significant costs from the delay, or irreparable harm such as credit damage.18Internal Revenue Service. IRM 13.1.7 TAS Case Criteria Request help with Form 911 by mail, fax, or email, or call 877-777-4778.
If You Disagree With the Decision
You can appeal. The letter explaining the IRS decision includes instructions and a deadline, usually 30 days from the date of that letter. Send your written protest to the address on the letter, not directly to the IRS Independent Office of Appeals; the examination unit gets a chance to reconsider before forwarding your case.19Internal Revenue Service. Preparing a Request for Appeals
If the total additional tax and penalties for the period in question are $25,000 or less, you can use the Small Case Request process with Form 12203 or a brief written statement listing each item you disagree with and why. Above $25,000, a formal written protest must include a statement of facts, the law you rely on, and the specific changes you’re contesting. IRS Publication 5 walks through both.19Internal Revenue Service. Preparing a Request for Appeals