A more thorough explanation:

Definition: An official mark or seal placed on a document, especially to show that a required tax, such as duty or excise tax, has been paid.

Example: When you buy a pack of cigarettes, there is a small stamp on the bottom of the pack that shows the tax has been paid.

Explanation: The stamp on the cigarette pack is an official mark that shows the required tax has been paid. This helps the government keep track of how much tax they are collecting from the sale of cigarettes.