Question

why is the postage stamp attached to each letter​

Answer 1

Explanation:

People buy stamps as a way to pay for the service of mailing a letter or package. They attach stamps to letters and packages before sending them. The postal service cancels, or marks, stamps before delivering the mail. The purpose of cancellation is to prevent people from using the same stamp a second time

Answer 2

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It is proof that the letter or package you are sending has been paid for. ... Without a stamp system sending a letter or package across the country or world would be a far more complex job than what it is today.