In the United States, a standard Forever stamp is a postage stamp with no printed dollar amount. A genuine, unused standard Forever stamp remains valid for the postage required for a one-ounce domestic First-Class Mail letter, even when postage prices rise. No extra postage is needed solely because that rate increases.

To mail an eligible letter weighing up to 1 oz, use a flat, flexible, rectangular envelope that meets current letter-size requirements. Write the recipient's address on the front and your return address in the upper left, seal the envelope, and attach the stamp in the upper right. Place the letter in an outgoing mailbox or collection box, or take it to a post office.

Heavier, oversized, square, rigid or uneven envelopes may require additional postage or a different mail service. International mail, postcards and other stamp types follow different postage rules. Check the stamp type, your mailpiece's weight and dimensions, and current mailing requirements before sending.