SASE Envelope: What It Is, How to Prepare One, and When You Need It

If someone asks you to "include a SASE," they want you to send an envelope addressed to yourself, with a stamp already attached. The recipient uses it to mail something back to you without spending their own money on postage. It is one of the simplest things to prepare, but getting the size and postage right can save you frustration.

This guide covers exactly what a SASE is, what size to use, how much postage to put on it, and step-by-step instructions for preparing one correctly.

Quick Answer: What Is a SASE Envelope?

A SASE (self-addressed stamped envelope) is an envelope you address to yourself and attach postage to before handing it to someone else, so they can mail a reply back to you at no cost to them. Most SASEs use a standard #9 envelope tucked inside a #10 outer envelope. The stamp goes on the SASE itself, not just on the outer mailing envelope.

• SASE = an envelope with your address on the front and a stamp already attached
• Most common SASE size: a #9 envelope (3 7/8 x 8 7/8 inches) inside a #10 outer envelope
• Postage on the SASE: $0.82 for a first-class 1 oz letter (USPS rate, July 12, 2026)
• Leave the SASE unsealed so the recipient can insert their reply
• Required for: manuscript submissions, autograph requests, contests, rebates, charity replies
• International mail: use an International Reply Coupon (IRC) instead of a US stamp

Browse #9 envelopes or #10 envelopes to stock up on the right size for your SASE needs.

What Does SASE Mean?

SASE stands for Self-Addressed Stamped Envelope. The term breaks down exactly as it reads: the envelope is addressed to yourself (self-addressed), and it already has a stamp on it (stamped). When you send a SASE to someone, you are handling their reply postage in advance so they can send something back to you without any extra effort or cost on their part.

You may also see the following variations of the term:

• SSAE (Stamped Self-Addressed Envelope): same meaning, different word order
• SAE (Stamped Addressed Envelope): common usage in the United Kingdom
• Reply-paid envelope: a broader term that includes business reply envelopes and SASEs

All three terms describe the same thing: an envelope ready to go, addressed to you, with postage already on it. The person you send it to just adds their content, seals it, and drops it in the mail.

When Is a SASE Required?

A SASE comes up in several situations where the recipient needs a way to reply but cannot or will not pay for their own postage. Knowing which situations call for one helps you prepare in advance.

Common situations that require a SASE:

• Manuscript and query letter submissions to literary agents and small publishers
• Fan mail and autograph requests sent to celebrities, athletes, or musicians
• Contest and sweepstakes entries that offer a free mail-in alternative to purchase
• Rebate claims for products that still use physical mail-in programs
• Nonprofit and charity replies when the organization cannot cover postage costs
• Requests for records or printed materials from government agencies or schools

Literary Agent and Publisher Submissions

Many literary agents and small publishers still accept physical query letters and manuscript pages. Their submission guidelines typically ask for a SASE so they can return a rejection or request letter, a marked-up manuscript, or contracts. If you skip the SASE, you may not receive a reply at all. Always check the specific agent's submission page for their current requirements, since some have moved to email-only submissions.

Fan Mail and Autograph Requests

When writing to athletes, musicians, or actors to request a signed photo or autograph, most fan mail instructions ask you to include a SASE. The celebrity or their management team will not pay to ship the item back to you. A SASE with appropriate postage for a small package or a flat gives them an easy, no-cost way to fulfill your request.

Contest and Sweepstakes Entries

Federal rules require some sweepstakes operators to provide a free alternative to purchasing entry. In those cases, a mail-in entry with a SASE is the required method. The company uses the SASE to send you the alternative entry form or confirmation. Always read the official rules carefully to see if a SASE is needed and what size or format they require.

Rebate Claims

Some product rebate programs still use physical mail. The instructions may ask you to include a SASE so the company can return your rebate check or confirmation. Digital rebates are now more common, but certain brands and retailers still rely on mail-based processes.

Nonprofit and Charity Communications

Small nonprofits and community organizations often ask donors or volunteers to include a SASE when writing in. Because many operate on tight budgets, they rely on SASEs to cover the cost of mailing replies, receipts, or membership materials.

Requesting Information or Records

Government agencies, schools, and businesses may request a SASE when you write asking for printed records, certificates, or informational materials. The SASE allows them to fulfill the request without billing you separately for postage.

What Size Envelope Do You Use for a SASE?

The right SASE size depends on what the recipient will need to return to you. Most SASEs use one of two standard sizes: a #9 or a #10 envelope.

The #9 envelope is the most common SASE choice. It is slightly narrower and shorter than a standard #10 business envelope, which means it slides neatly inside a #10 without folding. A single sheet of paper, a rejection letter, or a signed contract page fits inside a #9 easily.

If the person needs to return something bulkier, such as a form with attachments or a multi-page document, use a #10 as your SASE and mail it inside a #11 envelope, which measures 4 1/2 x 10 3/8 inches.

For manuscript pages or signed photos that should not be folded, a flat mailer works better than a standard business envelope. In those cases, check the submission or fan mail guidelines for specific size requirements.

Shop #9 envelopes at Business Envelopes and #10 envelopes at Business Envelopes to find the right size for your SASE.

How to Prepare a SASE: Step by Step

Preparing a SASE takes about two minutes. Follow these steps in order to make sure it is correct before you seal it inside your outgoing envelope.

1. Choose the right envelope size. Pick a #9 for a single-sheet reply or a #10 for something larger. Match the size to what the recipient will need to return.
2. Write your full name and mailing address in the center of the envelope. This is the delivery address on the SASE. It tells the postal carrier where to deliver it when it comes back to you. Use your full name, street address, city, state, and ZIP code on three clear lines.
3. Leave the return address area blank or write your name only. Because the SASE is already going back to you, the delivery address and your return address are the same. Some people leave the top-left corner blank; others write their name as a precaution so the carrier knows who sent the envelope.
4. Affix a first-class stamp in the top-right corner. Use a current $0.82 stamp for a standard 1 oz letter (USPS rate, effective July 12, 2026). Do not put the stamp on the outer envelope only. The stamp must be on the SASE itself since it will be mailed separately when the recipient uses it.
5. Leave the SASE unsealed. The recipient needs to be able to insert their reply before sealing. Do not glue, lick, or peel-and-press the envelope closure when you prepare it.
6. Fold the SASE neatly and place it inside your outgoing envelope. If you are using a #9 SASE inside a #10, fold the SASE in thirds so it fits flat. Place the SASE and your letter together in the outer envelope.
7. Address and stamp the outer mailing envelope. The outer envelope gets the recipient's address on the front and your return address in the top left. It also needs its own $0.82 stamp to cover your letter going to the recipient.
8. Seal the outer envelope and mail it. The sealed outer envelope carries your letter and the unsealed SASE together. The recipient opens it, reads your letter, places their reply inside the SASE, seals the SASE, and mails it back to you.

Need a self-sealing option? Self-seal envelopes skip the licking step and seal cleanly with pressure, which is useful if you are preparing a large batch of outgoing mailers.

What Postage Do You Put on a SASE in 2026?

As of July 12, 2026, USPS first-class postage for a standard 1 oz letter is $0.82 per stamp. That rate applies to envelopes weighing up to 1 oz, sized between 3 1/2 x 5 inches (minimum) and 6 1/8 x 11 1/2 inches (maximum).

An empty #9 or #10 envelope weighs about 0.1 to 0.15 oz on its own. Adding a single standard sheet of paper brings the total well under 1 oz, so one $0.82 stamp covers the return trip for most SASEs.

A few postage tips to keep in mind:

• Buy forever stamps. USPS forever stamps are always valid for one first-class letter, even if the rate goes up after you purchase them. They are the safest choice for SASEs you prepare in advance.
• Weigh heavier replies. If the recipient will be returning multiple pages or a card inside the SASE, weigh the expected return contents at the post office or with a postal scale before deciding on postage. Going over 1 oz requires an additional $0.29 per ounce.
• Check the envelope shape. Non-standard shapes, including square envelopes or rigid items, may trigger a $0.49 non-machinable surcharge. Standard #9 and #10 envelopes are machinable, so no surcharge applies.

Do You Seal a SASE Before Sending It?

No. Leave the SASE unsealed when you place it in your outgoing envelope. The whole point of a SASE is for the recipient to insert their reply before sealing it. If you seal the SASE beforehand, the recipient has to open it to use it, which defeats the purpose and may damage the envelope.

The correct flow is:

• You prepare the SASE with your address and a stamp, but leave it unsealed
• You seal the outer envelope (the one going to the recipient) around your letter and the unsealed SASE
• The recipient opens the outer envelope, reads your letter, places their reply inside the SASE, seals the SASE, and drops it in the mail

If you are using a peel-and-seal envelope as your SASE, keep the protective strip attached but do not press it closed. The recipient peels the strip and seals it before mailing.

SASE vs. Business Reply Envelope: What Is the Difference?

A SASE and a business reply envelope (BRE) serve the same function, but the payment model is completely different.

If you are an individual sending a manuscript query or a fan letter, a SASE is the right choice. If you run a business and mail hundreds of invoices or donation requests, a business reply envelope program may save money because you only pay postage when someone actually sends a reply.

Can You Use a SASE for International Mail?

A US postage stamp is not valid for international return mail. If you are writing to someone in another country and need them to reply, a SASE with a US stamp will not work because the recipient's postal service will not honor US postage.

The standard alternative for international correspondence is an International Reply Coupon (IRC). An IRC is a voucher sold at US post offices that the recipient in another country can exchange for return postage. USPS still sells IRCs, though availability at individual post offices varies. Call ahead or check the USPS website before visiting.

A few points to know about international SASEs:

• IRCs are redeemable in countries that participate in the Universal Postal Union (UPU)
• Not all countries accept IRCs, so confirm before purchasing
• Include a self-addressed envelope along with the IRC so the recipient does not have to address one themselves
• For autograph requests to international celebrities, many fan mail guides recommend including two or more IRCs to cover the weight of a signed photo

Where to Buy Envelopes for a SASE

The most common SASE envelopes are plain white business envelopes in standard sizes. You want consistent, clean envelopes that feed through postal sorting equipment without issues and give a professional appearance when your reply arrives.

#9 envelopes from Business Envelopes are the right size for most SASEs. They are available blank or custom-printed, in single boxes or bulk quantities with no minimum order required. If you send a lot of mail and want the option to include a pre-printed return address on your SASE, custom printing saves time compared to hand-addressing or using a rubber stamp.

For a slightly larger return envelope, #10 envelopes work well when the recipient needs to return more than one page. They also come blank or custom-printed with your return address already on the front.

If you prefer a modern peel-and-seal closure, self-seal envelopes give the recipient a clean, easy-to-close option without needing to lick the flap.

The Simple Version: You Pre-Pay, They Reply

A SASE removes friction. You pay the return postage in advance so the person receiving your letter has no reason not to reply. Whether you are reaching out to a literary agent, collecting autographs, or entering a contest, preparing a SASE correctly (right size, right postage, unsealed) shows you know how the process works and makes it easy for the recipient to follow through.

Keep a supply of #9 envelopes and #10 envelopes on hand so you are always ready to prepare a SASE without a last-minute trip to the store. Business Envelopes ships with no minimum order required, so you can order exactly what you need.