A paper tax return does not have one universal stamp count. One ordinary Forever stamp covers a standard rectangular domestic letter weighing no more than one ounce, but multi-page returns often weigh more. Weigh the sealed envelope, determine whether it is a letter or large envelope, and verify the exact IRS mailing address for your form, state and whether a payment is enclosed.
Current stamp counts for a letter-size tax return
| Sealed letter weight | 2026 postage | Ordinary Forever stamps only | Lower-overpayment option |
|---|---|---|---|
| Up to 1 oz | $0.82 | 1 | 1 Forever stamp |
| Over 1 oz through 2 oz | $1.11 | 2 ($1.64) | 1 Forever + 29¢ |
| Over 2 oz through 3 oz | $1.40 | 2 ($1.64) | 1 Forever + 58¢ |
| Over 3 oz through 3.5 oz | $1.69 | 3 ($2.46) | 2 Forever + 5¢ |
These figures apply only when the finished piece qualifies as a stamped First-Class Mail letter. A letter over 3.5 ounces must use another price category.
If you use a large envelope
An unfolded return in a large envelope is priced as a First-Class Mail flat only when it meets the flat standards. Current retail flat postage starts at $1.69 for one ounce, then rises with weight: $1.98 for two ounces, $2.27 for three ounces and $2.56 for four ounces. A rigid, nonrectangular or unevenly thick large envelope can be charged as a parcel instead.
Do not choose the large-envelope price merely because the envelope looks large. Measure, weigh and inspect the sealed piece, then use exact postage or the USPS calculator.
Verify the tax mailing address before adding postage
- Identify the exact tax form and tax year.
- Use the current IRS Where to File instructions for your state.
- Choose the address that matches whether a payment is enclosed.
- Copy the address exactly and add a complete return address.
- Check the filing deadline and mailing instructions that apply to your return.
IRS addresses can differ by form, location and payment status. An address from an old return, a general web page or another taxpayer may be wrong.
Should you use Certified Mail?
USPS recommends considering a service that provides proof of mailing for important tax documents. Certified Mail adds a mailing receipt and electronic delivery or attempted-delivery verification; Return Receipt is optional and costs extra. It does not replace the base postage. See the current Certified Mail stamp and fee calculation before choosing whole Forever stamps.
Keep your mailing receipt and a copy of the return. The choice of service depends on the record you need; this page explains postage and mailing mechanics, not tax-filing advice.
Final mailing checklist
- Sign every form that requires a signature.
- Attach only the documents requested by the form instructions.
- Keep sensitive data covered and seal the envelope securely.
- Weigh the completely assembled envelope.
- Use the correct current IRS address.
- Apply enough postage and obtain the mailing record you need.
Frequently asked questions
Is one Forever stamp enough for a tax return?
Only if the sealed piece qualifies as a standard letter and weighs no more than one ounce. Many multi-page returns exceed that weight.
Can I use two Forever stamps on my tax return?
Two current Forever stamps provide $1.64. They cover a qualifying letter through three ounces but overpay. They are still short of the $1.69 price for a 3.5-ounce letter or one-ounce large envelope.
Can I fold the return to use a regular envelope?
Follow the tax form’s filing instructions. If folding is permitted, a letter-size envelope may cost less, but its sealed weight and thickness still determine postage.
Does a postmark prove I filed on time?
Filing-deadline rules are determined by the IRS and applicable law. Use current IRS instructions and keep the mailing documentation appropriate for your situation.
Rates and mailing references checked September 1, 2026: USPS tax-mailing guidance; IRS Where to File; USPS Notice 123. Addresses, rates and rules can change.