The first known use of plenary indulgences was in 1095 when Pope Urban II remitted all penance of persons who participated in the crusades and who confessed their sins. Later, the indulgences were also offered to those who couldn't go on the Crusades but offered cash contributions to the effort instead.

When did indulgences start and end?

While reasserting the place of indulgences in the salvific process, the Council of Trent condemned “all base gain for securing indulgences” in 1563, and Pope Pius V abolished the sale of indulgences in 1567.

What were indulgences in the Middle Ages?

One particularly well-known Catholic method of exploitation in the Middle Ages was the practice of selling indulgences, a monetary payment of penalty which, supposedly, absolved one of past sins and/or released one from purgatory after death.