What is a piece of paper blessed by a churchman that said the owner was forgiven for their sins called?

A piece of paper blessed by a churchman that stated the owner was forgiven for their sins is called an "indulgence." During the Middle Ages, indulgences were sold by the Church as a way to reduce punishment for sins, both in this life and in the afterlife. This practice became controversial and was one of the factors leading to the Protestant Reformation.