When you mail a federal tax return, the envelope needs a signed Form 1040, every W-2 you received, any Form 1099 or W-2G that shows federal tax withheld, all the schedules and forms that support the numbers on your 1040, and — if you owe money — a check made out to United States Treasury along with Form 1040-V. Knowing what to include when mailing your tax return also means knowing what stays loose, what gets stapled, and what order the pages go in, because IRS processing centers scan returns with automated equipment and the order matters.
The Signed Form 1040
Form 1040 is the core of the filing. It reports your income, deductions, credits, and either the tax you owe or the refund you’re claiming.1Internal Revenue Service. About Form 1040, U.S. Individual Income Tax Return Print it clearly from the IRS website. Smudged or faint printing causes scanning errors. If you were born before January 2, 1961, you can use Form 1040-SR instead, which has larger type and a standard deduction chart printed on it.2Internal Revenue Service. Instructions 1040 (2025)
Sign and date the bottom of page two. If you’re filing jointly, both spouses have to sign. Without a signature, the return is not valid, and a missing signature is one of the most common reasons the IRS sends returns back.2Internal Revenue Service. Instructions 1040 (2025) By signing, you’re declaring under penalty of perjury that everything on the return is true and complete; intentionally filing a false return can result in fines up to $100,000 and up to three years in prison.3Office of the Law Revision Counsel. 26 USC 7206 – Fraud and False Statements
Income Documents to Attach
Staple every Form W-2 you received from employers to the front of the return.4Internal Revenue Service. Topic No. 301, When, How and Where to File If any Form 1099 or Form W-2G shows federal income tax was withheld, attach those to the front as well. The IRS uses these documents to verify that the withholding you reported on Line 25 of Form 1040 matches what your employer or payer actually sent in. Missing a W-2 is one of the fastest ways to trigger a notice.
Schedules and Supporting Forms
Any schedule that supports a line on your 1040 has to be included. The most common are Schedule A (itemized deductions), Schedule B (interest and dividends), Schedule C (business income), and Schedule D (capital gains). Place all schedules and forms behind the 1040 in the order of the Attachment Sequence Number printed in the upper-right corner of each form, not alphabetically. Supporting statements go behind the schedule they relate to.5Internal Revenue Service. 2025 Instructions for Form 1040
If you or a family member enrolled in health coverage through the Marketplace and received advance premium tax credits, you also need to complete Form 8962 and attach it. You’ll need the Form 1095-A that the Marketplace sends by January 31 to fill it out.6Internal Revenue Service. 2025 Instructions for Form 8962 – Premium Tax Credit (PTC) Skipping Form 8962 when you received advance credits will hold up your refund and generate IRS correspondence.
Payment Materials if You Owe
If your return shows a balance due, include a check or money order and Form 1040-V, the payment voucher. The voucher helps the IRS match your payment to your account. Fill in your Social Security number, the amount you’re paying, and your name and address.7Internal Revenue Service. About Form 1040-V, Payment Voucher for Individuals
Make the check payable to “United States Treasury,” not “IRS” or “Internal Revenue Service.” On the check itself, write your Social Security number, the tax year, and “Form 1040” so the payment can be traced if it separates from your return.8Internal Revenue Service. 2025 Form 1040-V Do not staple or paper-clip the check or voucher to the return or to each other. Put them loose in the envelope.9Internal Revenue Service. Pay by Check or Money Order Never send cash.
If you can’t pay in full, file the return on time anyway and consider requesting a monthly installment plan by completing Form 9465 and attaching it to the front of your return.10Internal Revenue Service. Where to File Your Taxes for Form 9465
How to Stack the Package
Order inside the envelope matters because IRS processing centers use automated scanning equipment. Stack everything this way:
- Form 1040 or 1040-SR: On top.
- W-2s and any income documents with withholding: Stapled to the front of the 1040.4Internal Revenue Service. Topic No. 301, When, How and Where to File
- Schedules and additional forms: Behind the 1040, in Attachment Sequence Number order (the number in the upper-right corner of each form).5Internal Revenue Service. 2025 Instructions for Form 1040
- Supporting statements: Behind the schedule they relate to.
- Form 1040-V and your check: Loose in the envelope. No staples, no paper clips.8Internal Revenue Service. 2025 Form 1040-V
Keep the State Return in Its Own Envelope
Your state income tax return does not go in the same envelope as your federal return. Federal returns go to the IRS; state returns go to your state’s tax agency at a completely different address. If you bundle them together, the IRS will not forward your state return. Mail each one separately, with the correct address and adequate postage on each.
The Envelope and Postage
The federal filing deadline for tax year 2025 returns is April 15, 2026. The mailing address for your return depends on the state you live in and whether you’re enclosing a payment. The IRS publishes the full table of addresses on its website and in the Form 1040 instructions.11Internal Revenue Service. Where to File Paper Tax Returns With or Without a Payment Using the wrong address will not invalidate the return, but it will delay processing.
Use enough postage. The IRS treats a return as filed on time only if the envelope has adequate postage, and returns with insufficient postage get sent back to you, potentially past the deadline.12USPS. Mail Your Tax Return with USPS A standard return with a few schedules usually weighs more than one ounce, so a single first-class stamp won’t cover it. Take the envelope to the post office counter and have it weighed.
A return mailed through the U.S. Postal Service is treated as filed on the postmark date, even if the IRS doesn’t receive it until days later.13Office of the Law Revision Counsel. 26 USC 7502 – Timely Mailing Treated as Timely Filing and Paying The postmark has to fall on or before the deadline, and the envelope must be properly addressed with prepaid postage. Send it by certified mail with a return receipt. The certified mail receipt is treated as prima facie evidence that the document was delivered to the IRS and gives you written proof of the mailing date.14USPS. Return Receipt – The Basics Keep it with your copy of the return.
Using FedEx, UPS, or DHL
You don’t have to use the Postal Service. The IRS has approved specific FedEx, UPS, and DHL services that qualify for the same timely-mailing rule, including options like FedEx Priority Overnight, UPS Next Day Air, and DHL Express. Only certain service tiers count; FedEx Ground, for example, is not on the list. Check the full IRS list before choosing a service.15Internal Revenue Service. Private Delivery Services (PDS)
If you use a private delivery service, you must send the return to the IRS submission processing center’s street address, not the P.O. box listed in the Form 1040 instructions. The three centers are in Austin, TX; Kansas City, MO; and Ogden, UT.16Internal Revenue Service. Submission Processing Center Street Addresses for Private Delivery Service (PDS) Private carriers can’t deliver to P.O. boxes.
Before You Seal the Envelope
Photocopy or scan every page you’re mailing: the 1040, every schedule, every W-2, the payment voucher, and the front and back of your check. Keep those copies with your certified mail receipt for at least three years, which is the standard IRS audit window for most returns. If anything goes wrong in processing, that paper trail is your proof that you filed correctly and on time.