Szczepan Walczynski
Szczepan Walczynski voted up Tom Jackson's answer


The pre-paid envelopes are charged to the addressee at a specific amount. 

The addressee may at a later date receive a credit for the amount of the stamp that you added to the envelope.

So you are eventually saving the addressee some money (which is why some nonprofits say your stamp "helps"), but it doesn't affect … Read more