What is postage due stamp?

A postage due stamp is a type of stamp used to indicate that the recipient of a mail item has not paid the required postage amount for its delivery. The stamp is affixed by the postal service to the envelope or package, and the recipient is charged with the amount due upon receipt.

Postage due stamps were first introduced in the United States in 1879, and they were used extensively during the late 19th and early 20th centuries. They were also used in other countries, including Canada and Great Britain.

Postage due stamps are typically smaller in size than regular postage stamps and often have a different design or color scheme. They may also include the words "postage due" or other similar phrasing.

Today, with the widespread use of electronic postage and automated mailing systems, postage due stamps are less commonly used. However, they are still occasionally used for packages or envelopes that have insufficient postage or are addressed incorrectly.