Written by Acorn Sales Company, manufacturing stamps and seals since 1964 · Reviewed by Holly R, VP of Sales and Marketing at Acorn Sales, against the USPS Domestic Mail Manual, USPS Business Mail 101, the MackayMitchell envelope size guide and the Acorn Sales address stamp and embosser listings on September 25, 2026 · Updated September 25, 2026
The return address goes in the upper left corner on the front of the envelope, on the same side as the delivery address. A 1-5/8″ square address stamp fits that corner on every standard size from an A2 invitation envelope to a #10 business envelope. Below are the USPS placement rules, a size chart for common envelopes, the areas to keep clear, and when an embosser suits better.
Where does the return address go on an envelope?
USPS tells mailers to "print or type your address in the upper-left corner on the front of the envelope," and to keep the address, return address and postage on the same side (USPS). The Domestic Mail Manual puts it formally: a domestic return address "must be placed in the upper left corner of the address side of the piece" (DMM 602.1.6).
USPS also asks that addresses be written parallel to the longest side (USPS). For a stamp, that simply means stamping with the text level along the top edge, not turned on its side.
Can you stamp the back flap instead?
As decoration, yes; as the return address, no. The back flap is not the address side, so it does not meet the DMM placement above. Acorn's address embosser listings describe the back flap as the place for "a special elegant touch," and that is the right way to think of it.
Some mail must carry a legible return address, including Priority Mail, Priority Mail Express, USPS Ground Advantage, Package Services and mail with extra services such as Registered or Insured Mail (DMM 602.1.5.3). For anything like that, put the return address on the front.
Envelope sizes and what fits
Sizes below are from the MackayMitchell envelope size guide. USPS treats a piece as letter size when it is between 5″ x 3-1/2″ and 11-1/2″ x 6-1/8″ and no more than 1/4″ thick (DMM 101.1.1).
| Envelope | Size (inches) | Within letter-size length and height? | 1-5/8″ square stamp in the corner? |
|---|---|---|---|
| A2 | 4-3/8 x 5-3/4 | Yes | Yes |
| A6 | 4-3/4 x 6-1/2 | Yes | Yes |
| A7 | 5-1/4 x 7-1/4 | Yes | Yes |
| A9 | 5-3/4 x 8-3/4 | Yes | Yes |
| #6-3/4 | 3-5/8 x 6-1/2 | Yes | Yes, with less room to spare |
| #9 | 3-7/8 x 8-7/8 | Yes | Yes |
| #10 | 4-1/8 x 9-1/2 | Yes | Yes |
| 9 x 12 catalog | 9 x 12 | No, larger than letter size | Yes |
| 10 x 13 catalog | 10 x 13 | No, larger than letter size | Yes |
Thickness counts too. A bulky card or a small gift can push an envelope past 1/4″ even when the length and height fit.
What part of the envelope should you keep clear?
Keep decorative stamps away from the delivery address and the strip along the bottom edge. USPS Business Mail 101 says "Don't put anything below the delivery line of the delivery address," because anything there "could confuse the machines and misdirect your mail" (USPS).
The bottom edge is also where USPS prints its barcode. The DMM defines a barcode clear zone running 4-3/4″ in from the right edge and 5/8″ up from the bottom, and printing there has to meet its reflectance standards (DMM 202). The simple rule: the upper left for your return address, and the lower right left alone.
Which address stamp size should you choose?
For personal mail, the 1-5/8″ square designer address stamps pair your address with a small illustration. They come in five bodies from $21.95 for a Shiny Duo hand stamp to $29.95 for Slim pre-inked, PSI pre-inked or wood handle versions.
For business envelopes, the plain text address stamps take three or four lines. The 3 Line Address Stamp Self Inking is $22.95 and the 4 Line Self Inking Address Stamp is $24.95, both set in 10 to 12 point type, above the 8 point minimum USPS recommends for a return address.
Stamp or embosser for envelopes?
An address embosser presses a raised impression with no ink. Acorn's address embosser plates measure 2″ wide by 1″ tall and take up to 26 characters per line, and all four embossers below carry a two year warranty.
| Embosser | Price | Reach from the edge | Paper |
|---|---|---|---|
| Handheld Address Embosser | $44.95 | About 1-1/2″ | One sheet of 20 to 24 lb paper, or light cardstock |
| Desk Address Embosser | $44.95 | About 1-1/2″ | Up to 40 lb paper for light cardstock or envelopes |
| Long Reach Desk Address Embosser | $129.95 | Up to 2-1/2″ | Up to 60 lb stock |
| Extended Long Reach Desk Address Embosser | $189.95 | Up to 4-1/2″ | Up to 60 lb stock |
Because an embossed impression has no ink, it reads by shadow rather than color. The embosser listings point to stationery and the back flap, so pair one with an inked return address on the front of the envelope.
Related guides
- Address and Return Address Stamps and Embossers
- Embossers: Complete Guide to Types, Uses and Ordering
- Return Address Stamp Wording: Examples That Fit on Three Lines
- Personalized Holiday Stamps: A Gift Guide and When to Order
- Embossing Seals for Envelopes: Design, Size and Style
Frequently asked questions
Where do you put the return address on an envelope?
In the upper left corner on the front, the same side as the delivery address and postage. The USPS Domestic Mail Manual says a domestic return address must be placed in the upper left corner of the address side.
Can the return address go on the back of the envelope?
Not as the official return address. USPS rules place it on the address side, so treat a back flap stamp or embossed impression as decoration and keep the return address on the front, especially on mail such as Priority Mail that requires one.
What size return address stamp fits a #10 envelope?
A 1-5/8″ square address stamp fits the upper left corner of a #10 envelope, which measures 4-1/8″ x 9-1/2″, with room left for the delivery address. For a plain business address, the three and four line self-inking stamps are made for business return addresses.
Is a return address required?
On many mail classes, yes. The DMM requires a legible return address on Priority Mail, Priority Mail Express, USPS Ground Advantage, Package Services and mail with extra services. USPS encourages mailers to use one so an undeliverable piece can come back to them.
What envelope sizes count as letters?
Pieces from 5″ x 3-1/2″ up to 11-1/2″ x 6-1/8″ and no more than 1/4″ thick. A2, A6, A7, A9, #6-3/4, #9 and #10 envelopes all fall inside those length and height limits; 9 x 12 and 10 x 13 catalog envelopes do not.
Can I emboss a return address on an envelope?
Yes. The Desk Address Embosser handles up to 40 lb paper for light cardstock or envelopes and reaches about 1-1/2″ from the edge. The long reach models reach 2-1/2″ or 4-1/2″ and take stock up to 60 lb.
Ready to set up your envelopes? Choose a design on our Address Stamps page.
