The act of nullifying or writing off the value of a postage stamp, rendering it unusable for further postage, typically occurs when it is affixed to an envelope or document. An example includes marking a stamp already used to prevent its reuse, often done without reliance on any battery-powered device.
Proper stamp invalidation is essential for maintaining the integrity of postal systems and preventing fraudulent use. Historically, techniques have evolved from simple pen marks to more sophisticated cancellations employing various inks and devices. This process safeguards revenue and ensures fair usage of postal services.