Most paper returns go out with two or three Forever stamps. One stamp covers the first ounce of a standard letter, and tax returns almost always weigh more than that, so the question of how many stamps to mail a tax return usually comes down to how many pages you’re sending and whether you’re using a regular envelope or a larger manila one.
A Forever stamp currently costs $0.78 and covers the first ounce of a standard letter-sized envelope. Each additional ounce adds $0.29.1U.S. Postal Service. U.S. Postal Service Recommends New Prices for July Because most returns run several pages, one stamp won’t be enough.2United States Postal Service. Mailing Your Tax Return
Standard Letter Envelope
A standard letter is no larger than 6⅛ by 11½ inches and tops out at 3.5 ounces.3USPS Postal Explorer. First-Class Mail Using Forever stamps:
- Up to 1 oz (roughly 4–5 pages): 1 stamp ($0.78)
- Up to 2 oz (roughly 10 pages): 2 stamps ($1.56 covers the $1.07 needed)
- Up to 3 oz (roughly 15 pages): 2 stamps ($1.56 covers the $1.36 needed)
- Up to 3.5 oz (the letter maximum): 3 stamps ($2.34 covers the $1.65 needed)
If your return is heavier than 3.5 ounces or won’t fit in a regular envelope, you’re in large-envelope territory, and the pricing changes.
Large Manila Envelope
Plenty of filers use a 9-by-12 or 10-by-13 manila envelope so they don’t have to fold the forms. Anything bigger than 6⅛ by 11½ inches, or thicker than ¼ inch, is a “flat” to the Postal Service and priced higher.4USPS Postal Explorer. Sizes for Large Envelopes and Flats Large envelopes start at $1.63 for the first ounce, with each additional ounce adding about $0.27 to $0.28.5United States Postal Service. Notice 123 – Price List In Forever stamps:
- Up to 2 oz: 3 stamps ($2.34 covers the $1.90 needed)
- Up to 3 oz: 3 stamps ($2.34 covers the $2.17 needed)
- Up to 4 oz: 4 stamps ($3.12 covers the $2.44 needed)
- Up to 6 oz: 4 stamps ($3.12 covers the $3.00 needed)
The manila envelope itself weighs close to an ounce, so remember to count the envelope along with the paper.
Weigh It or Take It to the Counter
A kitchen scale is enough to get you in the right bracket. If you don’t have one, walk the sealed envelope into a post office and have the clerk weigh it. Overpaying by a stamp costs you a dollar at most. Underpaying can cost far more, and here’s why.
Under federal law, a return is considered filed on the date it’s postmarked, not the date the IRS receives it.6Office of the Law Revision Counsel. 26 USC 7502 – Timely Mailing Treated as Timely Filing and Paying The rule only applies if the envelope has enough postage and is properly addressed. If your return goes out short on postage, one of two things happens: the Postal Service returns it to you stamped “Returned for Postage,” or it reaches the IRS with a deficiency notice, and the IRS can refuse to pay the shortage and send it back.7United States Postal Service. Domestic Mail Manual P011 – Payment Either way, when you finally remail it, the new postmark is your filing date. The original April 15 postmark doesn’t save you.
If You’re Mailing Close to the Deadline
Take the envelope directly to a post office counter and ask for a hand cancellation. That way the postmark is legible and shows the date you actually stood there. Collection boxes may not be emptied until the next morning, which can put a next-day postmark on a return you dropped off on time.
For proof that the return actually went out on the deadline, Certified Mail gives you a mailing receipt and tracking history. Adding a Return Receipt runs $4.40 for the physical green card or $2.82 for the electronic version, on top of regular postage and the Certified Mail fee.8United States Postal Service. Notice 123 – Price List Priority Mail is another option; it includes USPS Tracking and up to $100 of insurance and delivers in two to three business days.9United States Postal Service. Priority Mail Regular First-Class Mail delivers in one to five business days but doesn’t come with tracking.10United States Postal Service. First-Class Mail
A Note on Where It Goes
The IRS uses different mailing addresses depending on your state and whether you’re enclosing a payment.11Internal Revenue Service. Where to File Addresses for Taxpayers and Tax Professionals Filing Form 1040 The address doesn’t change how many stamps you need, but sending your return to the wrong center can delay processing by weeks. Check the current address in the Form 1040 instructions before you seal the envelope.
Why the Extra Stamp Is Worth It
The penalties for filing late aren’t small. If you owe tax and file late, the IRS charges 5% of the unpaid tax for each month the return is overdue, up to 25%.12Office of the Law Revision Counsel. 26 USC 6651 – Failure to File Tax Return or to Pay Tax A return more than 60 days late carries a minimum penalty of $525 or the full tax owed, whichever is smaller.13Internal Revenue Service. Failure to File Penalty There’s a separate 0.5% monthly penalty for paying late, also capped at 25%.
A $0.78 stamp against a $525 minimum penalty isn’t a close call. When you’re not sure whether the envelope crosses into the next weight bracket, add another stamp.