To send a letter to the IRS, put your name, address, taxpayer ID, and the relevant tax year at the top; if you’re answering a notice, include the CP or LTR number and use the response address printed on that notice; then mail it by USPS Certified Mail or an IRS-approved private delivery service so the postmark protects your filing date. Getting any of those three pieces wrong — the contents, the address, or the mailing method — can cost you a deadline or bury your case in the wrong processing center for months.
What to Put in the Letter
The IRS has to be able to match your letter to your account. Include your full legal name, your current mailing address, your Social Security Number or Individual Taxpayer Identification Number, and the tax year the letter concerns. Without those, your correspondence can sit unmatched.
If you’re responding to a notice, add the notice or letter number. It appears in the upper right corner of the document as a CP or LTR code.1Internal Revenue Service. Understanding Your IRS Notice or Letter Put it near the top of your letter so the person opening the envelope can route it correctly.
Sign and date the letter. An unsigned response can be treated as if you never sent it. Attach copies of any supporting documents — receipts, wage statements, bank records — and keep the originals plus a full copy of what you mailed.
If You’re Enclosing a Payment
Make the check or money order payable to “U.S. Treasury.” On the check itself, write your name and address, a daytime phone number, the tax year, the related form or notice number (for example, “2025 Form 1040”), and the SSN or ITIN of the person who should get credit for the payment.2Internal Revenue Service. Pay by Check or Money Order Don’t mail cash.
Two things to know. First, the address for a form with a payment is usually different from the address for the same form without one, because the IRS routes payments through separate centers. Second, the IRS may convert your check into an electronic fund transfer, so the money can leave your account the same day the letter is received.2Internal Revenue Service. Pay by Check or Money Order
Where to Mail It
There is no single IRS address. The right one depends on what you’re sending, whether a payment is enclosed, and where you live.
When You’re Answering a Notice
Use the response address printed on the notice itself. Don’t substitute another IRS address you’ve used before. Each notice type routes to a specific office, and picking the wrong one can add weeks or months.
When You’re Filing a Return or Form
Check the instructions for that specific form. Addresses vary by form, by whether you’re including a payment, and by your state. The IRS keeps a state-by-state directory for individual returns.3Internal Revenue Service. Where to File Paper Tax Returns With or Without a Payment A California resident filing Form 1040 without a payment, for instance, mails it to Ogden, Utah; the same return with a check goes to Louisville, Kentucky. Verify your state and form before sealing the envelope.
When You Live Abroad
If you’re overseas, using an APO or FPO address, or filing Form 2555 for the foreign earned income exclusion, the IRS uses separate addresses. Returns without a payment, or requesting a refund, go to the Austin, TX processing center; returns with a check or money order go to Charlotte, NC.4Internal Revenue Service. U.S. Citizens and Resident Aliens Abroad Where and When to File and Pay
How to Mail It So the Date Sticks
Under federal tax law, the postmark date counts as your filing date, even if the IRS opens the envelope days later.5Office of the Law Revision Counsel. 26 USC 7502 – Timely Mailing Treated as Timely Filing and Paying This “timely mailing, timely filing” rule only works if you use an approved method and the postmark falls on or before the deadline.
USPS Certified and Registered Mail
Certified Mail is the practical default. You get a tracking number, delivery confirmation, and a dated mailing receipt. Adding a Return Receipt gives you a signed record of when the IRS took delivery. The Taxpayer Advocate Service specifically recommends Certified Mail with a return receipt for paper tax returns.6Taxpayer Advocate Service. Options for Filing a Tax Return
Registered Mail gives you a stronger legal presumption. The statute treats registration as prima facie evidence that the document reached the IRS, and the registration date counts as the postmark date.5Office of the Law Revision Counsel. 26 USC 7502 – Timely Mailing Treated as Timely Filing and Paying It costs more and moves slower, so most people reserve it for filings where the money at stake justifies the expense.
Approved Private Delivery Services
The IRS designates specific service levels from DHL Express, FedEx, and UPS as qualifying for the timely-mailing rule. Only certain express and overnight tiers count; ground and economy options don’t. The full list of qualifying service levels is on the IRS website.7Internal Revenue Service. Private Delivery Services If you pick a non-qualifying service, your filing date becomes the day the IRS physically receives it, not the day you shipped it.
One more rule for private carriers: you have to send the package to a physical IRS street address, not a P.O. Box. The IRS publishes the correct street addresses for each processing center.8Internal Revenue Service. Submission Processing Center Street Addresses for Private Delivery Service
Letting Someone Else Send It for You
If you want a tax professional, attorney, or family member to handle correspondence with the IRS, you need a formal authorization. Form 2848, Power of Attorney and Declaration of Representative, lets a designated individual represent you before the IRS, including signing and mailing letters on your behalf.9Internal Revenue Service. Instructions for Form 2848 The person has to be eligible to practice before the IRS — an attorney, CPA, or enrolled agent.
If you only want someone to see your tax information without representing you, use Form 8821, Tax Information Authorization. Either way, appointing a representative doesn’t shift your tax liability. You still owe what you owe.9Internal Revenue Service. Instructions for Form 2848 Form 2848 can be submitted online through IRS.gov, by fax, or by mail; online is usually fastest.10Internal Revenue Service. Submit Forms 2848 and 8821 Online
After You Mail It
Keep the letter, attachments, and mailing receipt filed together. If you used Certified Mail or a private delivery service, use the tracking number to confirm the package arrived. That confirmation is your insurance if the IRS later says it never received anything.
Then wait. The IRS publishes a running list of which months’ correspondence it’s currently processing. In early 2026, the agency was working through individual general correspondence from December 2025, business correspondence from June 2025, and other correspondence from August 2025.11Internal Revenue Service. Processing Status for Tax Forms Response times routinely stretch past two months, and business backlogs can run six months or more. Check that page before calling; the IRS can’t tell you anything useful about a letter it hasn’t opened.
Don’t send a duplicate unless the IRS asks you to resubmit or the posted processing time has clearly passed. Duplicates create conflicts on your account and slow things down further.
What Happens If You Don’t Respond
Ignoring an IRS notice is one of the costliest mistakes a taxpayer can make. If you don’t respond to a notice proposing changes to your return, the IRS will typically assess the tax it thinks you owe and start collection. You lose the chance to dispute the amount or offer evidence.
The most time-sensitive notice is the Notice of Deficiency, sometimes called the “90-day letter” (CP3219N is one version). From the mailing date, you have 90 days to file a petition with the U.S. Tax Court challenging the proposed tax. If you live outside the United States, the window is 150 days.12Office of the Law Revision Counsel. 26 USC 6213 – Restrictions Applicable to Deficiencies; Petition to Tax Court Filing a tax return does not extend this deadline.13Internal Revenue Service. Understanding Your CP3219N Notice Miss it, and the IRS assesses the tax; your only path afterward is to pay first and pursue a refund through a harder process.
With other notices, no response can lead to penalty assessments, interest, federal tax liens, and eventually wage garnishments or bank levies. Your options are widest before the IRS moves from proposing a change to enforcing collection, and they narrow fast after that. Respond early, mail correctly, and keep proof of what you sent.