Postage Stamps and Buying Options: The Complete US Guide for 2026

A postage stamp is one of the smallest purchases in business, yet getting it wrong delays payments, returns legal documents, and stalls time-sensitive correspondence. This guide covers every current USPS stamp type, where to buy them, and how to match the right postage to the right envelope so nothing comes back to you.

Pair every letter with the right #10 envelope and you eliminate the two most common mailing mistakes in one step.

What is a Forever Stamp and how does it work?

USPS introduced the Forever stamp in 2007. The idea is simple: a Forever stamp always covers the current First-Class rate for a one-ounce domestic letter, no matter what you paid for it. A stamp bought years ago still mails a letter today at the current rate. You never need to buy adjustment stamps to top up old stock.

This makes Forever stamps the smart choice for any business that keeps stamp inventory. Stock up before a rate increase and every stamp in your drawer is still full-value postage. For most standard mailings, a Forever stamp on a #10 envelope is all you need.

Every USPS stamp type explained

First-Class Forever Stamps

The standard stamp for domestic one-ounce letters. Works for standard-size letters, greeting cards in A7 envelopes, and any flat mailpiece weighing one ounce or less. Available in sheets of 20, booklets of 20, and rolls of 100, 500, or 3,000 for high-volume mailers. Rolls are the practical choice for offices running weekly invoice or statement cycles through self seal envelopes.

Additional Ounce Stamps

Every ounce over the first adds to the cost of a First-Class letter. If you regularly mail multi-page documents, contracts, or anything with a return-reply enclosure, weigh the piece before assuming a single stamp covers it. An undelivered overweight letter costs far more in reprinting and delays than the extra stamp.

Postcard Stamps

Postcards mail at a lower rate than standard letters. To qualify for postcard rate, the piece must be between 3.5 × 5 inches and 4.25 × 6 inches and no thicker than 0.016 inches. Anything outside those dimensions mails as a letter at the full First-Class rate.

Global Forever Stamps

One Global Forever stamp covers a one-ounce letter to any country in the world. Canada, UK, Germany, Australia, Japan: all covered at one flat rate. Like the domestic Forever stamp, it never expires and always covers the then-current international one-ounce rate. For letters over one ounce internationally, weigh and calculate at a USPS counter or through Click-N-Ship.

Semipostal Stamps

Semipostal stamps cost slightly more than a standard Forever stamp. The extra amount above the First-Class rate goes to a designated charitable fund. They work as valid postage just like any other stamp.

Where to buy postage stamps

USPS Post Office

Every post office sells stamps at face value in singles, booklets, sheets, and rolls. Self-service kiosks at many locations let you buy stamps by credit card without waiting in line. The post office is the only place to buy specialty stamp rolls over the counter.

USPS.com Postal Store

The official USPS website carries over 100 stamp designs including themed collections, commemorative issues, and limited releases. Orders are mailed to your address. A good option if you want a specific design for wedding invitations or event mailings.

Grocery stores and pharmacies

CVS, Walgreens, Walmart, Target, and most major grocery chains sell Forever stamp booklets at face value through the USPS Stamps to Go program. Convenient for small purchases but selection is limited to standard booklets.

Amazon

Amazon sells USPS stamps in booklets and rolls through the official USPS store and authorized third-party sellers. Buy only from the official USPS listing or sellers with verified ratings to avoid counterfeits.

Online postage platforms

Stamps.com, Pitney Bowes PitneyShip, and USPS Click-N-Ship let you purchase and print postage directly from your computer. Metered rates through these platforms are typically lower than retail stamp rates. For businesses mailing more than 50 letters per week, the savings add up faster than the monthly platform fee.

How to choose the right stamp for your envelope

The stamp type you need depends on three things: weight, destination, and envelope size.

Standard #10 business letter: One First-Class Forever stamp covers a single sheet folded in thirds inside a standard #10 envelope. Add one additional ounce stamp for every ounce over one.

Window envelopes for invoices: One stamp per piece unless contents weigh over one ounce. Many businesses running high invoice volumes switch to metered postage to reduce cost per piece. Pair with window envelopes so the printed address shows through without double printing.

9×12 catalog envelopes with flat documents: Most single-sheet mailings in a 9×12 catalog envelope need one Forever stamp plus one additional ounce stamp at minimum. Always weigh before you seal.

A7 greeting card envelopes: Standard greeting cards usually need one stamp unless you include inserts or heavy cardstock.

International mail: Use one Global Forever stamp for any one-ounce letter to any country. Domestic stamps alone do not cover the international rate.

Oversized or square envelopes: Square envelopes trigger a non-machinable surcharge at USPS. This applies to any envelope with an aspect ratio between 1:1 and 1:1.3.

Checks and sensitive documents: Use check envelopes with security tinting so contents are not visible through the envelope. For documents that cannot arrive damaged, Tyvek envelopes are tear-proof, puncture-resistant, and moisture-resistant — worth the upgrade for legal filings, medical records, and contracts.

What makes Business Envelopes different

Business Envelopes has been supplying commercial envelopes to US offices, law firms, healthcare facilities, nonprofits, and direct mail operations since 1997. Here is what sets the catalog apart from general office supply retailers.

Depth of selection. Most office supply stores carry three or four envelope formats. Business Envelopes carries every commercial size from #6 3/4 through 10×15, in plain white, security tinted, window, double window, colored, Tyvek, kraft clasp, self-seal, and peel-and-seal configurations. If your mailing program has a specific format requirement, it is in the catalog.

Custom printing with real turnaround times. Return address, company logo, and full-color printing on any envelope in the catalog. PDF proof before production, nothing prints without your approval. Finished stock ships within 7 to 10 business days from proof approval.

Self-seal options in every standard size. Every major format at Business Envelopes is available in a self-seal configuration. The adhesive strip is protected until you peel the liner — no pre-sealing from humidity in storage.

Tyvek for documents that cannot arrive damaged. When a contract, legal filing, or medical record genuinely cannot arrive with a torn corner or moisture damage, Tyvek envelopes made from DuPont high-density polyethylene fiber are the right choice. Available in 6×9, 9×12, 10×13, and 10×15.

Free ground shipping on every order. No minimums, no thresholds. Every order ships free to the contiguous 48 states.

Why the right envelope matters as much as the stamp

A correctly stamped letter in the wrong envelope creates its own problems. An overweight mailing in an undersized envelope gets returned. A window envelope where the address block does not align with the cutout requires hand-addressing or reprinting. A paper envelope carrying a moisture-sensitive document arrives damaged.

The most common mismatches worth knowing:

Using a standard #10 for a two-page letter without checking the weight. Two sheets of 24 lb bond in a standard #10 envelope typically comes in just over one ounce. Add a return address enclosure and it is clearly over. One additional ounce stamp fixes it.

Using domestic stamps on international correspondence. The domestic rate does not cover international postage. A letter sent to London or Toronto with only a Forever stamp will be returned or delivered postage-due.

Using a paper catalog envelope for documents that need to arrive pristine. Thick reports, architectural drawings, and legal filings belong in a Tyvek envelope or clasp envelope, not a standard paper mailer.

Frequently asked questions

What is a Forever stamp?

 A Forever stamp always covers the current First-Class rate for a one-ounce domestic letter. It never expires and never needs to be topped up after a rate increase.

Do Forever stamps expire?

 No. Forever stamps have no expiration date and are always valid for one ounce of First-Class domestic postage regardless of when they were purchased.

How many stamps do I need for a 9×12 envelope?

 One Forever stamp plus one additional ounce stamp covers most single-document mailings in a 9×12 catalog envelope. Always weigh the sealed envelope to confirm.

Can I use Forever stamps for international mail?

 No. Domestic stamps alone do not cover the international rate. Use a Global Forever stamp or buy the correct international postage at a USPS counter or through Click-N-Ship.

What is a non-machinable surcharge? 

USPS charges extra for letters that cannot be processed by automated equipment. Square envelopes and pieces with an unusual aspect ratio all trigger the surcharge.

Where is the best place to buy stamps? 

USPS post offices, grocery stores, pharmacies, and Amazon all sell stamps at face value. Online postage platforms offer lower metered rates but require a monthly subscription fee that only makes sense for businesses mailing regularly at volume.

What type of envelope should I use with a Forever stamp? 

For standard business letters, a #10 envelope is the correct match. For invoices, use a window envelope. For unfolded documents, use a catalog envelope. For sensitive documents, use Tyvek envelopes.