When you mail a federal tax return, the envelope needs to contain Form 1040 (or 1040-SR) with any required schedules, Copy B of every W-2 and any other income form showing federal tax withheld, your handwritten signature, and — if you owe money — a check made out to “United States Treasury” along with Form 1040-V. That is what to send when filing taxes by mail. Everything else you received during the year, from 1099-INTs to health coverage forms, generally stays in your files. Getting the package right the first time matters because the IRS takes six or more weeks to process a paper return.
Form 1040 and the Schedules Behind It
Every individual paper filer starts with Form 1040, the return used to report annual income to the IRS.1Internal Revenue Service. About Form 1040, U.S. Individual Income Tax Return If you were born before January 2, 1961, you can use Form 1040-SR instead; it works the same way but uses larger print and includes a standard deduction chart for older filers.2Internal Revenue Service. Instructions for Form 1040 (2025) Download whichever form matches the current tax year from IRS.gov so you are not working from an outdated version.
The form asks for your Social Security number, your spouse’s if you file jointly, and each dependent’s number. An incorrect or missing number can reduce your refund or cause the IRS to deny credits like the child tax credit.2Internal Revenue Service. Instructions for Form 1040 (2025) Check that every name and number matches the Social Security cards.
Depending on your situation, one or more schedules go behind the main form:
- Schedule A if you itemize deductions instead of taking the standard deduction, listing items like medical expenses, state and local taxes, and mortgage interest.3Internal Revenue Service. 2025 Instructions for Schedule A (Form 1040) – Itemized Deductions
- Schedule C to report income or loss from a business or freelance work you operated as a sole proprietor.4Internal Revenue Service. About Schedule C (Form 1040), Profit or Loss from Business (Sole Proprietorship)
- Schedule 1 if you have additional income such as unemployment, alimony, or rental income, or above-the-line deductions like student loan interest or educator expenses.
- Schedule 8812 to claim the child tax credit or the additional child tax credit.
Each schedule has a small Attachment Sequence Number printed in the upper right corner. Stack the schedules in that numerical order behind Form 1040.
Which Income Documents to Attach
Paper returns need proof of income and taxes withheld. The most important document is Form W-2. The IRS specifically requires you to attach Copy B of every W-2 to the front of your return.5Internal Revenue Service. Topic No. 301, When, How and Where to File The agency uses these to verify that the withholding you claim matches what your employer sent to the Treasury. If you worked more than one job, attach a W-2 from each employer.
Beyond W-2s, attach any other income form that shows a dollar amount in the federal tax withheld box. The most common is Form 1099-R for retirement account distributions with tax withheld.6Internal Revenue Service. Instructions for Forms 1099-R and 5498 (2025) Form W-2G for gambling winnings with withholding attaches as well. These documents act as receipts proving you have already paid part of your tax bill.
What to Leave Out
A common mistake is stuffing the envelope with every tax form that arrived during the year. Most 1099 forms, including 1099-INT for bank interest, 1099-DIV for dividends, and 1099-NEC for freelance income, do not need to be attached unless they show federal tax withheld. You still use the numbers on these forms to complete your return, but the physical copies stay in your files.
Health insurance forms follow the same rule. Do not attach Form 1095-A, 1095-B, or 1095-C to your return.7Internal Revenue Service. Questions and Answers About Health Care Information Forms for Individuals If you received advance premium tax credits through a Marketplace plan, you will use Form 1095-A to complete Form 8962, which does get attached. The 1095-A itself stays home.
Signing the Return
An unsigned paper return is not a valid return. The IRS will send it back and ask for a signature, which can delay processing by weeks or months.8Internal Revenue Service. Policy Statement P-3-5 You must handwrite your signature on a paper return; typed or digital signatures are not accepted for mailed filings.2Internal Revenue Service. Instructions for Form 1040 (2025)
If you file jointly, both spouses must sign, even if only one had income during the year.2Internal Revenue Service. Instructions for Form 1040 (2025) If the IRS has issued you an Identity Protection PIN, enter that six-digit number in the space next to the signature line.9Internal Revenue Service. IRS Online Account and Identity Protection PINs Protect Against Identity Thieves and Scammers
Payment Voucher and Check If You Owe
If your return shows a balance due, include a payment with Form 1040-V. The voucher tells the IRS who the payment is from and which tax year it covers so they can credit the money to the right account.10Internal Revenue Service. About Form 1040-V, Payment Voucher for Individuals
Make your check or money order payable to “United States Treasury.” On the check itself, write your Social Security number, the tax year (2025 for returns filed in 2026), and “Form 1040.”11Internal Revenue Service. Pay by Check or Money Order That information is a backup if the check gets separated from the voucher during processing. Do not use staples or paper clips to attach the payment or voucher to your return; place them loosely in the envelope.12Internal Revenue Service. Form 1040-V (2025) Never send cash.
How to Assemble the Package
Once everything is filled out and signed, organize the envelope contents in this order:
- Copies of all W-2s, W-2Gs, and any other forms showing federal withholding, stapled to the front of Form 1040.5Internal Revenue Service. Topic No. 301, When, How and Where to File
- Form 1040 (or 1040-SR) itself.
- Schedules and forms behind the main form, arranged in Attachment Sequence Number order.
- Any supporting statements last, in the same order as the schedules they support.
- Form 1040-V and your check or money order, loose in the envelope and not attached to the return.
Staple the W-2 copies to the front of Form 1040 and staple the schedules together behind it. Keep the payment voucher and check unstapled so the IRS can separate them during processing.
Address, Postage, and Proof of Mailing
The IRS uses different mailing addresses depending on your state of residence and whether you are enclosing a payment. Returns with a payment go to a different processing center than returns without one.13Internal Revenue Service. Where to File Paper Tax Returns With or Without a Payment Sending your return to the wrong address can delay processing significantly. Look up the correct address on the IRS website right before you mail, since addresses can change year to year.
If you live outside the United States, use an APO or FPO address, or file Form 2555 for foreign earned income, you have a separate designated address. Returns without payment go to Austin, TX 73301-0215, and returns with payment go to P.O. Box 1303, Charlotte, NC 28201-1303.14Internal Revenue Service. International – Where to File Form 1040 Addresses for Taxpayers and Tax Professionals
A tax return with a few schedules and W-2s can easily exceed one ounce, so weigh your envelope or take it to the post office to avoid having it returned for insufficient postage. A first-class stamp costs $0.78 and covers letters up to one ounce.15USPS. 2026 Postage Price Change First-class letters can weigh up to 3.5 ounces; anything heavier goes as a large envelope or flat.16USPS. First-Class Mail
Sending your return by USPS Certified Mail with a return receipt gives you a legal record of the mailing date. Under federal law, the postmark on your envelope counts as the official filing date even if the IRS receives the package days later.17Office of the Law Revision Counsel. 26 USC 7502 – Timely Mailing Treated as Timely Filing and Paying That proof can protect you from late-filing penalties if the IRS later disputes when you filed.
Certain IRS-approved private delivery services from DHL Express, FedEx, and UPS qualify for the same timely-mailing rule, but only specific service levels are on the list. Standard ground services like FedEx Ground and UPS Ground are not approved.18Internal Revenue Service. Private Delivery Services (PDS) If you use a private carrier, send your return to the IRS street address published for private deliveries rather than to a PO box.19Internal Revenue Service. Submission Processing Center Street Addresses for Private Delivery Service (PDS)
If You Are Mailing an Amended Return
Amended returns are a separate case. If you discover an error after mailing your original return, you correct it with Form 1040-X, and amended returns have their own mailing addresses that differ from those used for original returns.20Internal Revenue Service. Where to File Addresses for Taxpayers and Tax Professionals Filing Form 1040-X Your destination depends on which state you live in, with processing centers in Kansas City, Austin, and Ogden handling different regions. Attach any new or corrected forms that support the changes, such as a corrected W-2 or a schedule you previously omitted.