Guide
Do I need a stamp to mail a letter?
If you're dropping a letter in a mailbox or handing it to a postal carrier, yes—you need postage. Without it, your letter won't be delivered.
Published Jan 14, 2026 • Updated Jan 21, 2026
How postage works
Every piece of mail in the USPS system requires postage. This pays for sorting, transportation, and delivery to the recipient's address.
For most standard letters, a single First-Class stamp covers it. For heavier or larger items, you need more postage.
Current postage rates
Postage rates change periodically. Check the USPS price list for the current rates that apply to your mailpiece type:
- Standard letters (1 oz, #10 envelope)
- Additional ounces (letters over 1 oz)
- Large envelopes (flats)
- Postcards
Note: Forever Stamps bought at any price remain valid for First-Class letters regardless of future increases.
What counts as "1 ounce"?
A standard #10 envelope with 4-5 sheets of regular paper weighs about 1 ounce. If you're mailing more pages, thicker paper, or anything besides paper, weigh it.
Post offices have scales. Many shipping stores and office supply stores do too. When in doubt, add an extra stamp.
What happens if you don't use enough postage
Returned to sender — The most common outcome. USPS returns the letter to your return address marked "Postage Due" or "Insufficient Postage."
Delivered postage due — Sometimes USPS delivers the letter and charges the recipient for the missing postage. This is embarrassing and annoying for everyone involved.
Letter sits in limbo — Without a return address and without enough postage, mail can end up in a dead letter office.
Always use the right amount of postage and always include a return address.
Where to buy stamps
Post office — Most reliable. Available at the counter or from self-service kiosks.
Grocery stores and pharmacies — Many sell books of stamps near the checkout. Usually limited to Forever Stamps.
Online at USPS.com — Stamps delivered to your address in a few days.
Amazon and other retailers — Often at or slightly above face value.
Forever Stamps explained
Forever Stamps are sold at the current first-class rate but remain valid forever, even if rates go up. If you bought stamps at $0.55 years ago, they still work for a standard letter today.
They're called "Forever" because they don't have a denomination printed on them—just "FOREVER."
Alternatives to traditional stamps
Metered mail — Businesses often use postage meters that print postage directly on envelopes. Requires a meter rental.
Printed postage — Services like Stamps.com or Pirate Ship let you print USPS postage labels at home. Requires a printer and scale.
Online mailing services — PostalForm and similar services handle postage as part of the service. You don't buy stamps separately.
If you don't have stamps
You have a few options:
- Buy stamps — Post office, store, or online
- Go to the post office — They can weigh your letter and apply the correct postage at the counter
- Mail online — Upload a PDF to PostalForm and we handle printing, envelope, and postage
Common questions
Can I use old stamps?
Yes. Forever Stamps never expire. Older denominated stamps can be combined to reach the current rate (e.g., use a $0.55 stamp + a $0.18 stamp to make $0.73).
Can I mail without a stamp if I put "Postage Paid" on it?
No. "Postage Paid" indicia are only valid when printed by authorized postage systems. Writing it by hand does nothing.
What if I'm mailing internationally?
International rates are different and higher. Check USPS.com for rates by destination. A single Forever Stamp isn't enough for international mail.
Can the recipient pay postage?
Only if you use a Business Reply envelope (preprinted with permit info). You can't just write "recipient pays" on an envelope.
Skip stamps entirely
If you're mailing a letter and don't have stamps—or don't want to deal with them—upload a PDF to PostalForm. We print your letter, put it in an envelope, apply postage, and mail it via USPS.