Yes, you can fold your tax return. The IRS’s own mail-handling guidance calls for documents to be folded into letter-size envelopes whenever folding will not damage the contents, with photographs the only noted exception.1Internal Revenue Service. 1.22.2 United States Postal Service Classes of Mail, USPS Additional Services and Small Package Carrier Services A folded Form 1040 in a standard business envelope is accepted and routinely processed, so long as the return is signed, assembled correctly, addressed to the right service center, and carries enough postage.
Folding Into a Standard Business Envelope
A #10 business envelope handles a basic Form 1040 with a few pages of schedules. Fold the pages into three roughly equal sections so they sit flat without bunching. Ordinary creases do not interfere with IRS scanning as long as the paper is not torn or heavily wrinkled.
If you use a window envelope, line up the IRS service center address with the transparent opening so it stays visible in transit. A misaligned address can send the envelope back to you.
Postage matters. A first-class stamp costs $0.78 in 2026, but most returns weigh more than one ounce even folded.2USPS. 2026 Postage Price Change Weigh the envelope on a kitchen scale or hand it to a postal clerk. Returns sent with insufficient postage come back to you rather than moving on to the IRS.3USPS. Mail Your Tax Return with USPS
Mailing Flat in a Large Envelope
If your return runs to many schedules or supporting documents, a 9×12 or 10×13 envelope lets you skip folding entirely. Flat returns are also easier for IRS staff to sort when the packet is thick.
Large envelopes cost more. First-class postage for a large envelope starts at $1.63 and rises with weight.4USPS. First-Class Mail and Postage The first-class large envelope category caps at 13 ounces and three-quarters of an inch thick. Over either limit, you need Priority Mail or another service.
Assembling the Return Before You Seal It
Every schedule and form has an attachment sequence number printed in its upper-right corner. Stack them behind Form 1040 in order of those numbers.5Internal Revenue Service. Topic No. 301, When, How and Where to File Attach copies of your W-2s, W-2Gs, and any 1099-Rs showing federal withholding to the front of the 1040, in the area marked “Attach Form(s) W-2 here.”6Internal Revenue Service. Form 1040 (2025) Do not staple anything in the space at the very top of page one, which is reserved for IRS use.
Sign the return by hand. Digital, electronic, or typed-font signatures do not count, and an unsigned return can be treated as unfiled, which can trigger late-filing penalties.7Internal Revenue Service. Instructions for Form 1040 (2025) Joint filers both need to sign. Date the return and fill in the occupation field for each filer.
If You Are Mailing a Payment
Owe tax? Fill out Form 1040-V and place it in the envelope with your check or money order. Do not staple or paper-clip the payment or voucher to the return or to each other; all three items sit loose in the envelope.8Internal Revenue Service. Form 1040-V Payment Voucher for Individuals (2025) The mailing address for returns with a payment is different from the address for returns without one, so verify before sealing.
Where to Send It
The correct address depends on the state you live in and whether you are enclosing a payment. The IRS publishes a full state-by-state table, and the Form 1040 instructions list the address for your state as well.9Internal Revenue Service. Where to File Paper Tax Returns With or Without a Payment Sending your return to the wrong service center delays processing.
Filers abroad, those using an APO or FPO address, or anyone filing Form 2555 use a separate set of addresses. Returns without a payment go to Austin, TX 73301-0215; returns with a payment go to P.O. Box 1303, Charlotte, NC 28201-1303.10Internal Revenue Service. International – Where to File Form 1040 Addresses for Taxpayers and Tax Professionals
The Postmark Counts as Your Filing Date
The federal filing deadline for tax year 2025 returns is April 15, 2026.3USPS. Mail Your Tax Return with USPS Under federal law, the USPS postmark on your envelope is your filing date, even if the IRS does not physically receive the return until days later.11Office of the Law Revision Counsel. 26 U.S. Code 7502 – Timely Mailing Treated as Timely Filing and Paying The return qualifies as on time if it is properly addressed, carries enough postage, and is postmarked on or before the deadline.12USPS. Mailing Your Tax Return If you send it by registered mail, the registration date serves as the postmark.
Missing the deadline triggers a late-filing penalty of 5% of your unpaid tax for each month or partial month the return is late, up to 25%.13Internal Revenue Service. Get the Facts About Late Filing and Late Payment Penalties Paper returns take roughly six weeks to process, compared with about 21 days for e-filed returns, so build in time if you are expecting a refund.5Internal Revenue Service. Topic No. 301, When, How and Where to File
Getting Proof You Mailed It
The IRS recommends sending paper returns by certified mail with a return receipt. The receipt documents both the mailing date and the date the IRS received it.14Taxpayer Advocate Service. Options for Filing a Tax Return Keep the receipt somewhere safe; USPS does not store copies.3USPS. Mail Your Tax Return with USPS
Certain private delivery services also qualify under the timely-mailing-as-timely-filing rule. Approved options include specific tiers from FedEx (such as Priority Overnight and Standard Overnight), UPS (such as Next Day Air and 2nd Day Air), and DHL Express.15Internal Revenue Service. Private Delivery Services (PDS) Not every service tier from these carriers counts, so check the IRS list before choosing one.
Keep a Copy
Before you seal the envelope, photocopy or scan the signed return, every schedule, and every attachment. The IRS recommends keeping copies of filed returns to help prepare future filings and to support any amended returns.16Internal Revenue Service.