Ordinary personal letters normally need prepaid postage before they enter the mail.
Prepaid packaging and labels
A Priority Mail Flat Rate envelope includes the packaging format but still requires the applicable Priority Mail postage or label; ‘Flat Rate’ does not mean free mailing. ReadyPost packaging is merchandise and normally does not include postage. A USPS Ground Advantage shipping label can pay the applicable package postage, so additional stamps are not needed when the label is valid and fully covers the service. Always distinguish packaging from proof of payment.
Ordinary household letters
A qualifying one-ounce domestic stamped letter currently requires 82¢. Heavier, nonmachinable, large, international, or service-enhanced mail needs a different amount.
Stamped envelopes and prepaid mail
Some envelopes or reply pieces already include postage. Check the indicium or instructions rather than adding another stamp automatically.
What happens without enough postage
Mail may be returned, delayed, or assessed postage due. When uncertain, have the completed item checked before mailing.
Frequently asked questions
Can I mail a letter without a stamp?
Only if postage is paid by another accepted method or the mailpiece is legitimately prepaid.
Does a return address replace postage?
No.
How much postage does an ordinary letter need?
82¢ for a qualifying one-ounce domestic stamped letter.
Sources and update note
- USPS Notice 123 — current price list
- USPS DMM 101 — physical standards
- USPS DMM 604 — postage payment methods
Rates and mailing standards can change. This page was reviewed in August 2026; verify the completed mailpiece when its weight, dimensions, shape, destination, or services are uncertain.
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